Mon, 01 Dec 2014 15:24:56 +0100
8075210: Refactor strong root processing in order to allow G1 to evolve separately from GenCollectedHeap
Summary: Create a G1RootProcessor and move SharedHeap root processing to GenCollectedHeap
Reviewed-by: brutisso, tschatzl, ehelin
1 /*
2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
25 #if !defined(__clang_major__) && defined(__GNUC__)
26 #define ATTRIBUTE_PRINTF(x,y) // FIXME, formats are a mess.
27 #endif
29 #include "precompiled.hpp"
30 #include "classfile/metadataOnStackMark.hpp"
31 #include "code/codeCache.hpp"
32 #include "code/icBuffer.hpp"
33 #include "gc_implementation/g1/bufferingOopClosure.hpp"
34 #include "gc_implementation/g1/concurrentG1Refine.hpp"
35 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
36 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
37 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
38 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
39 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
40 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
41 #include "gc_implementation/g1/g1EvacFailure.hpp"
42 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
43 #include "gc_implementation/g1/g1Log.hpp"
44 #include "gc_implementation/g1/g1MarkSweep.hpp"
45 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
46 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
47 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
48 #include "gc_implementation/g1/g1RemSet.inline.hpp"
49 #include "gc_implementation/g1/g1RootProcessor.hpp"
50 #include "gc_implementation/g1/g1StringDedup.hpp"
51 #include "gc_implementation/g1/g1YCTypes.hpp"
52 #include "gc_implementation/g1/heapRegion.inline.hpp"
53 #include "gc_implementation/g1/heapRegionRemSet.hpp"
54 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
55 #include "gc_implementation/g1/vm_operations_g1.hpp"
56 #include "gc_implementation/shared/gcHeapSummary.hpp"
57 #include "gc_implementation/shared/gcTimer.hpp"
58 #include "gc_implementation/shared/gcTrace.hpp"
59 #include "gc_implementation/shared/gcTraceTime.hpp"
60 #include "gc_implementation/shared/isGCActiveMark.hpp"
61 #include "memory/allocation.hpp"
62 #include "memory/gcLocker.inline.hpp"
63 #include "memory/generationSpec.hpp"
64 #include "memory/iterator.hpp"
65 #include "memory/referenceProcessor.hpp"
66 #include "oops/oop.inline.hpp"
67 #include "oops/oop.pcgc.inline.hpp"
68 #include "runtime/orderAccess.inline.hpp"
69 #include "runtime/vmThread.hpp"
71 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
73 // turn it on so that the contents of the young list (scan-only /
74 // to-be-collected) are printed at "strategic" points before / during
75 // / after the collection --- this is useful for debugging
76 #define YOUNG_LIST_VERBOSE 0
77 // CURRENT STATUS
78 // This file is under construction. Search for "FIXME".
80 // INVARIANTS/NOTES
81 //
82 // All allocation activity covered by the G1CollectedHeap interface is
83 // serialized by acquiring the HeapLock. This happens in mem_allocate
84 // and allocate_new_tlab, which are the "entry" points to the
85 // allocation code from the rest of the JVM. (Note that this does not
86 // apply to TLAB allocation, which is not part of this interface: it
87 // is done by clients of this interface.)
89 // Local to this file.
91 class RefineCardTableEntryClosure: public CardTableEntryClosure {
92 bool _concurrent;
93 public:
94 RefineCardTableEntryClosure() : _concurrent(true) { }
96 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
97 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
98 // This path is executed by the concurrent refine or mutator threads,
99 // concurrently, and so we do not care if card_ptr contains references
100 // that point into the collection set.
101 assert(!oops_into_cset, "should be");
103 if (_concurrent && SuspendibleThreadSet::should_yield()) {
104 // Caller will actually yield.
105 return false;
106 }
107 // Otherwise, we finished successfully; return true.
108 return true;
109 }
111 void set_concurrent(bool b) { _concurrent = b; }
112 };
115 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
116 size_t _num_processed;
117 CardTableModRefBS* _ctbs;
118 int _histo[256];
120 public:
121 ClearLoggedCardTableEntryClosure() :
122 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
123 {
124 for (int i = 0; i < 256; i++) _histo[i] = 0;
125 }
127 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
128 unsigned char* ujb = (unsigned char*)card_ptr;
129 int ind = (int)(*ujb);
130 _histo[ind]++;
132 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
133 _num_processed++;
135 return true;
136 }
138 size_t num_processed() { return _num_processed; }
140 void print_histo() {
141 gclog_or_tty->print_cr("Card table value histogram:");
142 for (int i = 0; i < 256; i++) {
143 if (_histo[i] != 0) {
144 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
145 }
146 }
147 }
148 };
150 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
151 private:
152 size_t _num_processed;
154 public:
155 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
157 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
158 *card_ptr = CardTableModRefBS::dirty_card_val();
159 _num_processed++;
160 return true;
161 }
163 size_t num_processed() const { return _num_processed; }
164 };
166 YoungList::YoungList(G1CollectedHeap* g1h) :
167 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
168 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
169 guarantee(check_list_empty(false), "just making sure...");
170 }
172 void YoungList::push_region(HeapRegion *hr) {
173 assert(!hr->is_young(), "should not already be young");
174 assert(hr->get_next_young_region() == NULL, "cause it should!");
176 hr->set_next_young_region(_head);
177 _head = hr;
179 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
180 ++_length;
181 }
183 void YoungList::add_survivor_region(HeapRegion* hr) {
184 assert(hr->is_survivor(), "should be flagged as survivor region");
185 assert(hr->get_next_young_region() == NULL, "cause it should!");
187 hr->set_next_young_region(_survivor_head);
188 if (_survivor_head == NULL) {
189 _survivor_tail = hr;
190 }
191 _survivor_head = hr;
192 ++_survivor_length;
193 }
195 void YoungList::empty_list(HeapRegion* list) {
196 while (list != NULL) {
197 HeapRegion* next = list->get_next_young_region();
198 list->set_next_young_region(NULL);
199 list->uninstall_surv_rate_group();
200 // This is called before a Full GC and all the non-empty /
201 // non-humongous regions at the end of the Full GC will end up as
202 // old anyway.
203 list->set_old();
204 list = next;
205 }
206 }
208 void YoungList::empty_list() {
209 assert(check_list_well_formed(), "young list should be well formed");
211 empty_list(_head);
212 _head = NULL;
213 _length = 0;
215 empty_list(_survivor_head);
216 _survivor_head = NULL;
217 _survivor_tail = NULL;
218 _survivor_length = 0;
220 _last_sampled_rs_lengths = 0;
222 assert(check_list_empty(false), "just making sure...");
223 }
225 bool YoungList::check_list_well_formed() {
226 bool ret = true;
228 uint length = 0;
229 HeapRegion* curr = _head;
230 HeapRegion* last = NULL;
231 while (curr != NULL) {
232 if (!curr->is_young()) {
233 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
234 "incorrectly tagged (y: %d, surv: %d)",
235 curr->bottom(), curr->end(),
236 curr->is_young(), curr->is_survivor());
237 ret = false;
238 }
239 ++length;
240 last = curr;
241 curr = curr->get_next_young_region();
242 }
243 ret = ret && (length == _length);
245 if (!ret) {
246 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
247 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
248 length, _length);
249 }
251 return ret;
252 }
254 bool YoungList::check_list_empty(bool check_sample) {
255 bool ret = true;
257 if (_length != 0) {
258 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
259 _length);
260 ret = false;
261 }
262 if (check_sample && _last_sampled_rs_lengths != 0) {
263 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
264 ret = false;
265 }
266 if (_head != NULL) {
267 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
268 ret = false;
269 }
270 if (!ret) {
271 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
272 }
274 return ret;
275 }
277 void
278 YoungList::rs_length_sampling_init() {
279 _sampled_rs_lengths = 0;
280 _curr = _head;
281 }
283 bool
284 YoungList::rs_length_sampling_more() {
285 return _curr != NULL;
286 }
288 void
289 YoungList::rs_length_sampling_next() {
290 assert( _curr != NULL, "invariant" );
291 size_t rs_length = _curr->rem_set()->occupied();
293 _sampled_rs_lengths += rs_length;
295 // The current region may not yet have been added to the
296 // incremental collection set (it gets added when it is
297 // retired as the current allocation region).
298 if (_curr->in_collection_set()) {
299 // Update the collection set policy information for this region
300 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
301 }
303 _curr = _curr->get_next_young_region();
304 if (_curr == NULL) {
305 _last_sampled_rs_lengths = _sampled_rs_lengths;
306 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
307 }
308 }
310 void
311 YoungList::reset_auxilary_lists() {
312 guarantee( is_empty(), "young list should be empty" );
313 assert(check_list_well_formed(), "young list should be well formed");
315 // Add survivor regions to SurvRateGroup.
316 _g1h->g1_policy()->note_start_adding_survivor_regions();
317 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
319 int young_index_in_cset = 0;
320 for (HeapRegion* curr = _survivor_head;
321 curr != NULL;
322 curr = curr->get_next_young_region()) {
323 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
325 // The region is a non-empty survivor so let's add it to
326 // the incremental collection set for the next evacuation
327 // pause.
328 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
329 young_index_in_cset += 1;
330 }
331 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
332 _g1h->g1_policy()->note_stop_adding_survivor_regions();
334 _head = _survivor_head;
335 _length = _survivor_length;
336 if (_survivor_head != NULL) {
337 assert(_survivor_tail != NULL, "cause it shouldn't be");
338 assert(_survivor_length > 0, "invariant");
339 _survivor_tail->set_next_young_region(NULL);
340 }
342 // Don't clear the survivor list handles until the start of
343 // the next evacuation pause - we need it in order to re-tag
344 // the survivor regions from this evacuation pause as 'young'
345 // at the start of the next.
347 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
349 assert(check_list_well_formed(), "young list should be well formed");
350 }
352 void YoungList::print() {
353 HeapRegion* lists[] = {_head, _survivor_head};
354 const char* names[] = {"YOUNG", "SURVIVOR"};
356 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
357 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
358 HeapRegion *curr = lists[list];
359 if (curr == NULL)
360 gclog_or_tty->print_cr(" empty");
361 while (curr != NULL) {
362 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
363 HR_FORMAT_PARAMS(curr),
364 curr->prev_top_at_mark_start(),
365 curr->next_top_at_mark_start(),
366 curr->age_in_surv_rate_group_cond());
367 curr = curr->get_next_young_region();
368 }
369 }
371 gclog_or_tty->cr();
372 }
374 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
375 OtherRegionsTable::invalidate(start_idx, num_regions);
376 }
378 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
379 // The from card cache is not the memory that is actually committed. So we cannot
380 // take advantage of the zero_filled parameter.
381 reset_from_card_cache(start_idx, num_regions);
382 }
384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
385 {
386 // Claim the right to put the region on the dirty cards region list
387 // by installing a self pointer.
388 HeapRegion* next = hr->get_next_dirty_cards_region();
389 if (next == NULL) {
390 HeapRegion* res = (HeapRegion*)
391 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
392 NULL);
393 if (res == NULL) {
394 HeapRegion* head;
395 do {
396 // Put the region to the dirty cards region list.
397 head = _dirty_cards_region_list;
398 next = (HeapRegion*)
399 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
400 if (next == head) {
401 assert(hr->get_next_dirty_cards_region() == hr,
402 "hr->get_next_dirty_cards_region() != hr");
403 if (next == NULL) {
404 // The last region in the list points to itself.
405 hr->set_next_dirty_cards_region(hr);
406 } else {
407 hr->set_next_dirty_cards_region(next);
408 }
409 }
410 } while (next != head);
411 }
412 }
413 }
415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
416 {
417 HeapRegion* head;
418 HeapRegion* hr;
419 do {
420 head = _dirty_cards_region_list;
421 if (head == NULL) {
422 return NULL;
423 }
424 HeapRegion* new_head = head->get_next_dirty_cards_region();
425 if (head == new_head) {
426 // The last region.
427 new_head = NULL;
428 }
429 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
430 head);
431 } while (hr != head);
432 assert(hr != NULL, "invariant");
433 hr->set_next_dirty_cards_region(NULL);
434 return hr;
435 }
437 #ifdef ASSERT
438 // A region is added to the collection set as it is retired
439 // so an address p can point to a region which will be in the
440 // collection set but has not yet been retired. This method
441 // therefore is only accurate during a GC pause after all
442 // regions have been retired. It is used for debugging
443 // to check if an nmethod has references to objects that can
444 // be move during a partial collection. Though it can be
445 // inaccurate, it is sufficient for G1 because the conservative
446 // implementation of is_scavengable() for G1 will indicate that
447 // all nmethods must be scanned during a partial collection.
448 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
449 if (p == NULL) {
450 return false;
451 }
452 return heap_region_containing(p)->in_collection_set();
453 }
454 #endif
456 // Returns true if the reference points to an object that
457 // can move in an incremental collection.
458 bool G1CollectedHeap::is_scavengable(const void* p) {
459 HeapRegion* hr = heap_region_containing(p);
460 return !hr->isHumongous();
461 }
463 void G1CollectedHeap::check_ct_logs_at_safepoint() {
464 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
465 CardTableModRefBS* ct_bs = g1_barrier_set();
467 // Count the dirty cards at the start.
468 CountNonCleanMemRegionClosure count1(this);
469 ct_bs->mod_card_iterate(&count1);
470 int orig_count = count1.n();
472 // First clear the logged cards.
473 ClearLoggedCardTableEntryClosure clear;
474 dcqs.apply_closure_to_all_completed_buffers(&clear);
475 dcqs.iterate_closure_all_threads(&clear, false);
476 clear.print_histo();
478 // Now ensure that there's no dirty cards.
479 CountNonCleanMemRegionClosure count2(this);
480 ct_bs->mod_card_iterate(&count2);
481 if (count2.n() != 0) {
482 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
483 count2.n(), orig_count);
484 }
485 guarantee(count2.n() == 0, "Card table should be clean.");
487 RedirtyLoggedCardTableEntryClosure redirty;
488 dcqs.apply_closure_to_all_completed_buffers(&redirty);
489 dcqs.iterate_closure_all_threads(&redirty, false);
490 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
491 clear.num_processed(), orig_count);
492 guarantee(redirty.num_processed() == clear.num_processed(),
493 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
494 redirty.num_processed(), clear.num_processed()));
496 CountNonCleanMemRegionClosure count3(this);
497 ct_bs->mod_card_iterate(&count3);
498 if (count3.n() != orig_count) {
499 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
500 orig_count, count3.n());
501 guarantee(count3.n() >= orig_count, "Should have restored them all.");
502 }
503 }
505 // Private class members.
507 G1CollectedHeap* G1CollectedHeap::_g1h;
509 // Private methods.
511 HeapRegion*
512 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
513 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
514 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
515 if (!_secondary_free_list.is_empty()) {
516 if (G1ConcRegionFreeingVerbose) {
517 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
518 "secondary_free_list has %u entries",
519 _secondary_free_list.length());
520 }
521 // It looks as if there are free regions available on the
522 // secondary_free_list. Let's move them to the free_list and try
523 // again to allocate from it.
524 append_secondary_free_list();
526 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
527 "empty we should have moved at least one entry to the free_list");
528 HeapRegion* res = _hrm.allocate_free_region(is_old);
529 if (G1ConcRegionFreeingVerbose) {
530 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
531 "allocated "HR_FORMAT" from secondary_free_list",
532 HR_FORMAT_PARAMS(res));
533 }
534 return res;
535 }
537 // Wait here until we get notified either when (a) there are no
538 // more free regions coming or (b) some regions have been moved on
539 // the secondary_free_list.
540 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
541 }
543 if (G1ConcRegionFreeingVerbose) {
544 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
545 "could not allocate from secondary_free_list");
546 }
547 return NULL;
548 }
550 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
551 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
552 "the only time we use this to allocate a humongous region is "
553 "when we are allocating a single humongous region");
555 HeapRegion* res;
556 if (G1StressConcRegionFreeing) {
557 if (!_secondary_free_list.is_empty()) {
558 if (G1ConcRegionFreeingVerbose) {
559 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
560 "forced to look at the secondary_free_list");
561 }
562 res = new_region_try_secondary_free_list(is_old);
563 if (res != NULL) {
564 return res;
565 }
566 }
567 }
569 res = _hrm.allocate_free_region(is_old);
571 if (res == NULL) {
572 if (G1ConcRegionFreeingVerbose) {
573 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
574 "res == NULL, trying the secondary_free_list");
575 }
576 res = new_region_try_secondary_free_list(is_old);
577 }
578 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
579 // Currently, only attempts to allocate GC alloc regions set
580 // do_expand to true. So, we should only reach here during a
581 // safepoint. If this assumption changes we might have to
582 // reconsider the use of _expand_heap_after_alloc_failure.
583 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
585 ergo_verbose1(ErgoHeapSizing,
586 "attempt heap expansion",
587 ergo_format_reason("region allocation request failed")
588 ergo_format_byte("allocation request"),
589 word_size * HeapWordSize);
590 if (expand(word_size * HeapWordSize)) {
591 // Given that expand() succeeded in expanding the heap, and we
592 // always expand the heap by an amount aligned to the heap
593 // region size, the free list should in theory not be empty.
594 // In either case allocate_free_region() will check for NULL.
595 res = _hrm.allocate_free_region(is_old);
596 } else {
597 _expand_heap_after_alloc_failure = false;
598 }
599 }
600 return res;
601 }
603 HeapWord*
604 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
605 uint num_regions,
606 size_t word_size,
607 AllocationContext_t context) {
608 assert(first != G1_NO_HRM_INDEX, "pre-condition");
609 assert(isHumongous(word_size), "word_size should be humongous");
610 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
612 // Index of last region in the series + 1.
613 uint last = first + num_regions;
615 // We need to initialize the region(s) we just discovered. This is
616 // a bit tricky given that it can happen concurrently with
617 // refinement threads refining cards on these regions and
618 // potentially wanting to refine the BOT as they are scanning
619 // those cards (this can happen shortly after a cleanup; see CR
620 // 6991377). So we have to set up the region(s) carefully and in
621 // a specific order.
623 // The word size sum of all the regions we will allocate.
624 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
625 assert(word_size <= word_size_sum, "sanity");
627 // This will be the "starts humongous" region.
628 HeapRegion* first_hr = region_at(first);
629 // The header of the new object will be placed at the bottom of
630 // the first region.
631 HeapWord* new_obj = first_hr->bottom();
632 // This will be the new end of the first region in the series that
633 // should also match the end of the last region in the series.
634 HeapWord* new_end = new_obj + word_size_sum;
635 // This will be the new top of the first region that will reflect
636 // this allocation.
637 HeapWord* new_top = new_obj + word_size;
639 // First, we need to zero the header of the space that we will be
640 // allocating. When we update top further down, some refinement
641 // threads might try to scan the region. By zeroing the header we
642 // ensure that any thread that will try to scan the region will
643 // come across the zero klass word and bail out.
644 //
645 // NOTE: It would not have been correct to have used
646 // CollectedHeap::fill_with_object() and make the space look like
647 // an int array. The thread that is doing the allocation will
648 // later update the object header to a potentially different array
649 // type and, for a very short period of time, the klass and length
650 // fields will be inconsistent. This could cause a refinement
651 // thread to calculate the object size incorrectly.
652 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
654 // We will set up the first region as "starts humongous". This
655 // will also update the BOT covering all the regions to reflect
656 // that there is a single object that starts at the bottom of the
657 // first region.
658 first_hr->set_startsHumongous(new_top, new_end);
659 first_hr->set_allocation_context(context);
660 // Then, if there are any, we will set up the "continues
661 // humongous" regions.
662 HeapRegion* hr = NULL;
663 for (uint i = first + 1; i < last; ++i) {
664 hr = region_at(i);
665 hr->set_continuesHumongous(first_hr);
666 hr->set_allocation_context(context);
667 }
668 // If we have "continues humongous" regions (hr != NULL), then the
669 // end of the last one should match new_end.
670 assert(hr == NULL || hr->end() == new_end, "sanity");
672 // Up to this point no concurrent thread would have been able to
673 // do any scanning on any region in this series. All the top
674 // fields still point to bottom, so the intersection between
675 // [bottom,top] and [card_start,card_end] will be empty. Before we
676 // update the top fields, we'll do a storestore to make sure that
677 // no thread sees the update to top before the zeroing of the
678 // object header and the BOT initialization.
679 OrderAccess::storestore();
681 // Now that the BOT and the object header have been initialized,
682 // we can update top of the "starts humongous" region.
683 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
684 "new_top should be in this region");
685 first_hr->set_top(new_top);
686 if (_hr_printer.is_active()) {
687 HeapWord* bottom = first_hr->bottom();
688 HeapWord* end = first_hr->orig_end();
689 if ((first + 1) == last) {
690 // the series has a single humongous region
691 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
692 } else {
693 // the series has more than one humongous regions
694 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
695 }
696 }
698 // Now, we will update the top fields of the "continues humongous"
699 // regions. The reason we need to do this is that, otherwise,
700 // these regions would look empty and this will confuse parts of
701 // G1. For example, the code that looks for a consecutive number
702 // of empty regions will consider them empty and try to
703 // re-allocate them. We can extend is_empty() to also include
704 // !continuesHumongous(), but it is easier to just update the top
705 // fields here. The way we set top for all regions (i.e., top ==
706 // end for all regions but the last one, top == new_top for the
707 // last one) is actually used when we will free up the humongous
708 // region in free_humongous_region().
709 hr = NULL;
710 for (uint i = first + 1; i < last; ++i) {
711 hr = region_at(i);
712 if ((i + 1) == last) {
713 // last continues humongous region
714 assert(hr->bottom() < new_top && new_top <= hr->end(),
715 "new_top should fall on this region");
716 hr->set_top(new_top);
717 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
718 } else {
719 // not last one
720 assert(new_top > hr->end(), "new_top should be above this region");
721 hr->set_top(hr->end());
722 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
723 }
724 }
725 // If we have continues humongous regions (hr != NULL), then the
726 // end of the last one should match new_end and its top should
727 // match new_top.
728 assert(hr == NULL ||
729 (hr->end() == new_end && hr->top() == new_top), "sanity");
730 check_bitmaps("Humongous Region Allocation", first_hr);
732 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
733 _allocator->increase_used(first_hr->used());
734 _humongous_set.add(first_hr);
736 return new_obj;
737 }
739 // If could fit into free regions w/o expansion, try.
740 // Otherwise, if can expand, do so.
741 // Otherwise, if using ex regions might help, try with ex given back.
742 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
743 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
745 verify_region_sets_optional();
747 uint first = G1_NO_HRM_INDEX;
748 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
750 if (obj_regions == 1) {
751 // Only one region to allocate, try to use a fast path by directly allocating
752 // from the free lists. Do not try to expand here, we will potentially do that
753 // later.
754 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
755 if (hr != NULL) {
756 first = hr->hrm_index();
757 }
758 } else {
759 // We can't allocate humongous regions spanning more than one region while
760 // cleanupComplete() is running, since some of the regions we find to be
761 // empty might not yet be added to the free list. It is not straightforward
762 // to know in which list they are on so that we can remove them. We only
763 // need to do this if we need to allocate more than one region to satisfy the
764 // current humongous allocation request. If we are only allocating one region
765 // we use the one-region region allocation code (see above), that already
766 // potentially waits for regions from the secondary free list.
767 wait_while_free_regions_coming();
768 append_secondary_free_list_if_not_empty_with_lock();
770 // Policy: Try only empty regions (i.e. already committed first). Maybe we
771 // are lucky enough to find some.
772 first = _hrm.find_contiguous_only_empty(obj_regions);
773 if (first != G1_NO_HRM_INDEX) {
774 _hrm.allocate_free_regions_starting_at(first, obj_regions);
775 }
776 }
778 if (first == G1_NO_HRM_INDEX) {
779 // Policy: We could not find enough regions for the humongous object in the
780 // free list. Look through the heap to find a mix of free and uncommitted regions.
781 // If so, try expansion.
782 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
783 if (first != G1_NO_HRM_INDEX) {
784 // We found something. Make sure these regions are committed, i.e. expand
785 // the heap. Alternatively we could do a defragmentation GC.
786 ergo_verbose1(ErgoHeapSizing,
787 "attempt heap expansion",
788 ergo_format_reason("humongous allocation request failed")
789 ergo_format_byte("allocation request"),
790 word_size * HeapWordSize);
792 _hrm.expand_at(first, obj_regions);
793 g1_policy()->record_new_heap_size(num_regions());
795 #ifdef ASSERT
796 for (uint i = first; i < first + obj_regions; ++i) {
797 HeapRegion* hr = region_at(i);
798 assert(hr->is_free(), "sanity");
799 assert(hr->is_empty(), "sanity");
800 assert(is_on_master_free_list(hr), "sanity");
801 }
802 #endif
803 _hrm.allocate_free_regions_starting_at(first, obj_regions);
804 } else {
805 // Policy: Potentially trigger a defragmentation GC.
806 }
807 }
809 HeapWord* result = NULL;
810 if (first != G1_NO_HRM_INDEX) {
811 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
812 word_size, context);
813 assert(result != NULL, "it should always return a valid result");
815 // A successful humongous object allocation changes the used space
816 // information of the old generation so we need to recalculate the
817 // sizes and update the jstat counters here.
818 g1mm()->update_sizes();
819 }
821 verify_region_sets_optional();
823 return result;
824 }
826 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
827 assert_heap_not_locked_and_not_at_safepoint();
828 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
830 unsigned int dummy_gc_count_before;
831 int dummy_gclocker_retry_count = 0;
832 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
833 }
835 HeapWord*
836 G1CollectedHeap::mem_allocate(size_t word_size,
837 bool* gc_overhead_limit_was_exceeded) {
838 assert_heap_not_locked_and_not_at_safepoint();
840 // Loop until the allocation is satisfied, or unsatisfied after GC.
841 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
842 unsigned int gc_count_before;
844 HeapWord* result = NULL;
845 if (!isHumongous(word_size)) {
846 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
847 } else {
848 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
849 }
850 if (result != NULL) {
851 return result;
852 }
854 // Create the garbage collection operation...
855 VM_G1CollectForAllocation op(gc_count_before, word_size);
856 op.set_allocation_context(AllocationContext::current());
858 // ...and get the VM thread to execute it.
859 VMThread::execute(&op);
861 if (op.prologue_succeeded() && op.pause_succeeded()) {
862 // If the operation was successful we'll return the result even
863 // if it is NULL. If the allocation attempt failed immediately
864 // after a Full GC, it's unlikely we'll be able to allocate now.
865 HeapWord* result = op.result();
866 if (result != NULL && !isHumongous(word_size)) {
867 // Allocations that take place on VM operations do not do any
868 // card dirtying and we have to do it here. We only have to do
869 // this for non-humongous allocations, though.
870 dirty_young_block(result, word_size);
871 }
872 return result;
873 } else {
874 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
875 return NULL;
876 }
877 assert(op.result() == NULL,
878 "the result should be NULL if the VM op did not succeed");
879 }
881 // Give a warning if we seem to be looping forever.
882 if ((QueuedAllocationWarningCount > 0) &&
883 (try_count % QueuedAllocationWarningCount == 0)) {
884 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
885 }
886 }
888 ShouldNotReachHere();
889 return NULL;
890 }
892 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
893 AllocationContext_t context,
894 unsigned int *gc_count_before_ret,
895 int* gclocker_retry_count_ret) {
896 // Make sure you read the note in attempt_allocation_humongous().
898 assert_heap_not_locked_and_not_at_safepoint();
899 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
900 "be called for humongous allocation requests");
902 // We should only get here after the first-level allocation attempt
903 // (attempt_allocation()) failed to allocate.
905 // We will loop until a) we manage to successfully perform the
906 // allocation or b) we successfully schedule a collection which
907 // fails to perform the allocation. b) is the only case when we'll
908 // return NULL.
909 HeapWord* result = NULL;
910 for (int try_count = 1; /* we'll return */; try_count += 1) {
911 bool should_try_gc;
912 unsigned int gc_count_before;
914 {
915 MutexLockerEx x(Heap_lock);
916 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
917 false /* bot_updates */);
918 if (result != NULL) {
919 return result;
920 }
922 // If we reach here, attempt_allocation_locked() above failed to
923 // allocate a new region. So the mutator alloc region should be NULL.
924 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
926 if (GC_locker::is_active_and_needs_gc()) {
927 if (g1_policy()->can_expand_young_list()) {
928 // No need for an ergo verbose message here,
929 // can_expand_young_list() does this when it returns true.
930 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
931 false /* bot_updates */);
932 if (result != NULL) {
933 return result;
934 }
935 }
936 should_try_gc = false;
937 } else {
938 // The GCLocker may not be active but the GCLocker initiated
939 // GC may not yet have been performed (GCLocker::needs_gc()
940 // returns true). In this case we do not try this GC and
941 // wait until the GCLocker initiated GC is performed, and
942 // then retry the allocation.
943 if (GC_locker::needs_gc()) {
944 should_try_gc = false;
945 } else {
946 // Read the GC count while still holding the Heap_lock.
947 gc_count_before = total_collections();
948 should_try_gc = true;
949 }
950 }
951 }
953 if (should_try_gc) {
954 bool succeeded;
955 result = do_collection_pause(word_size, gc_count_before, &succeeded,
956 GCCause::_g1_inc_collection_pause);
957 if (result != NULL) {
958 assert(succeeded, "only way to get back a non-NULL result");
959 return result;
960 }
962 if (succeeded) {
963 // If we get here we successfully scheduled a collection which
964 // failed to allocate. No point in trying to allocate
965 // further. We'll just return NULL.
966 MutexLockerEx x(Heap_lock);
967 *gc_count_before_ret = total_collections();
968 return NULL;
969 }
970 } else {
971 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
972 MutexLockerEx x(Heap_lock);
973 *gc_count_before_ret = total_collections();
974 return NULL;
975 }
976 // The GCLocker is either active or the GCLocker initiated
977 // GC has not yet been performed. Stall until it is and
978 // then retry the allocation.
979 GC_locker::stall_until_clear();
980 (*gclocker_retry_count_ret) += 1;
981 }
983 // We can reach here if we were unsuccessful in scheduling a
984 // collection (because another thread beat us to it) or if we were
985 // stalled due to the GC locker. In either can we should retry the
986 // allocation attempt in case another thread successfully
987 // performed a collection and reclaimed enough space. We do the
988 // first attempt (without holding the Heap_lock) here and the
989 // follow-on attempt will be at the start of the next loop
990 // iteration (after taking the Heap_lock).
991 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
992 false /* bot_updates */);
993 if (result != NULL) {
994 return result;
995 }
997 // Give a warning if we seem to be looping forever.
998 if ((QueuedAllocationWarningCount > 0) &&
999 (try_count % QueuedAllocationWarningCount == 0)) {
1000 warning("G1CollectedHeap::attempt_allocation_slow() "
1001 "retries %d times", try_count);
1002 }
1003 }
1005 ShouldNotReachHere();
1006 return NULL;
1007 }
1009 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1010 unsigned int * gc_count_before_ret,
1011 int* gclocker_retry_count_ret) {
1012 // The structure of this method has a lot of similarities to
1013 // attempt_allocation_slow(). The reason these two were not merged
1014 // into a single one is that such a method would require several "if
1015 // allocation is not humongous do this, otherwise do that"
1016 // conditional paths which would obscure its flow. In fact, an early
1017 // version of this code did use a unified method which was harder to
1018 // follow and, as a result, it had subtle bugs that were hard to
1019 // track down. So keeping these two methods separate allows each to
1020 // be more readable. It will be good to keep these two in sync as
1021 // much as possible.
1023 assert_heap_not_locked_and_not_at_safepoint();
1024 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1025 "should only be called for humongous allocations");
1027 // Humongous objects can exhaust the heap quickly, so we should check if we
1028 // need to start a marking cycle at each humongous object allocation. We do
1029 // the check before we do the actual allocation. The reason for doing it
1030 // before the allocation is that we avoid having to keep track of the newly
1031 // allocated memory while we do a GC.
1032 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1033 word_size)) {
1034 collect(GCCause::_g1_humongous_allocation);
1035 }
1037 // We will loop until a) we manage to successfully perform the
1038 // allocation or b) we successfully schedule a collection which
1039 // fails to perform the allocation. b) is the only case when we'll
1040 // return NULL.
1041 HeapWord* result = NULL;
1042 for (int try_count = 1; /* we'll return */; try_count += 1) {
1043 bool should_try_gc;
1044 unsigned int gc_count_before;
1046 {
1047 MutexLockerEx x(Heap_lock);
1049 // Given that humongous objects are not allocated in young
1050 // regions, we'll first try to do the allocation without doing a
1051 // collection hoping that there's enough space in the heap.
1052 result = humongous_obj_allocate(word_size, AllocationContext::current());
1053 if (result != NULL) {
1054 return result;
1055 }
1057 if (GC_locker::is_active_and_needs_gc()) {
1058 should_try_gc = false;
1059 } else {
1060 // The GCLocker may not be active but the GCLocker initiated
1061 // GC may not yet have been performed (GCLocker::needs_gc()
1062 // returns true). In this case we do not try this GC and
1063 // wait until the GCLocker initiated GC is performed, and
1064 // then retry the allocation.
1065 if (GC_locker::needs_gc()) {
1066 should_try_gc = false;
1067 } else {
1068 // Read the GC count while still holding the Heap_lock.
1069 gc_count_before = total_collections();
1070 should_try_gc = true;
1071 }
1072 }
1073 }
1075 if (should_try_gc) {
1076 // If we failed to allocate the humongous object, we should try to
1077 // do a collection pause (if we're allowed) in case it reclaims
1078 // enough space for the allocation to succeed after the pause.
1080 bool succeeded;
1081 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1082 GCCause::_g1_humongous_allocation);
1083 if (result != NULL) {
1084 assert(succeeded, "only way to get back a non-NULL result");
1085 return result;
1086 }
1088 if (succeeded) {
1089 // If we get here we successfully scheduled a collection which
1090 // failed to allocate. No point in trying to allocate
1091 // further. We'll just return NULL.
1092 MutexLockerEx x(Heap_lock);
1093 *gc_count_before_ret = total_collections();
1094 return NULL;
1095 }
1096 } else {
1097 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1098 MutexLockerEx x(Heap_lock);
1099 *gc_count_before_ret = total_collections();
1100 return NULL;
1101 }
1102 // The GCLocker is either active or the GCLocker initiated
1103 // GC has not yet been performed. Stall until it is and
1104 // then retry the allocation.
1105 GC_locker::stall_until_clear();
1106 (*gclocker_retry_count_ret) += 1;
1107 }
1109 // We can reach here if we were unsuccessful in scheduling a
1110 // collection (because another thread beat us to it) or if we were
1111 // stalled due to the GC locker. In either can we should retry the
1112 // allocation attempt in case another thread successfully
1113 // performed a collection and reclaimed enough space. Give a
1114 // warning if we seem to be looping forever.
1116 if ((QueuedAllocationWarningCount > 0) &&
1117 (try_count % QueuedAllocationWarningCount == 0)) {
1118 warning("G1CollectedHeap::attempt_allocation_humongous() "
1119 "retries %d times", try_count);
1120 }
1121 }
1123 ShouldNotReachHere();
1124 return NULL;
1125 }
1127 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1128 AllocationContext_t context,
1129 bool expect_null_mutator_alloc_region) {
1130 assert_at_safepoint(true /* should_be_vm_thread */);
1131 assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1132 !expect_null_mutator_alloc_region,
1133 "the current alloc region was unexpectedly found to be non-NULL");
1135 if (!isHumongous(word_size)) {
1136 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1137 false /* bot_updates */);
1138 } else {
1139 HeapWord* result = humongous_obj_allocate(word_size, context);
1140 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1141 g1_policy()->set_initiate_conc_mark_if_possible();
1142 }
1143 return result;
1144 }
1146 ShouldNotReachHere();
1147 }
1149 class PostMCRemSetClearClosure: public HeapRegionClosure {
1150 G1CollectedHeap* _g1h;
1151 ModRefBarrierSet* _mr_bs;
1152 public:
1153 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1154 _g1h(g1h), _mr_bs(mr_bs) {}
1156 bool doHeapRegion(HeapRegion* r) {
1157 HeapRegionRemSet* hrrs = r->rem_set();
1159 if (r->continuesHumongous()) {
1160 // We'll assert that the strong code root list and RSet is empty
1161 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1162 assert(hrrs->occupied() == 0, "RSet should be empty");
1163 return false;
1164 }
1166 _g1h->reset_gc_time_stamps(r);
1167 hrrs->clear();
1168 // You might think here that we could clear just the cards
1169 // corresponding to the used region. But no: if we leave a dirty card
1170 // in a region we might allocate into, then it would prevent that card
1171 // from being enqueued, and cause it to be missed.
1172 // Re: the performance cost: we shouldn't be doing full GC anyway!
1173 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1175 return false;
1176 }
1177 };
1179 void G1CollectedHeap::clear_rsets_post_compaction() {
1180 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1181 heap_region_iterate(&rs_clear);
1182 }
1184 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1185 G1CollectedHeap* _g1h;
1186 UpdateRSOopClosure _cl;
1187 int _worker_i;
1188 public:
1189 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1190 _cl(g1->g1_rem_set(), worker_i),
1191 _worker_i(worker_i),
1192 _g1h(g1)
1193 { }
1195 bool doHeapRegion(HeapRegion* r) {
1196 if (!r->continuesHumongous()) {
1197 _cl.set_from(r);
1198 r->oop_iterate(&_cl);
1199 }
1200 return false;
1201 }
1202 };
1204 class ParRebuildRSTask: public AbstractGangTask {
1205 G1CollectedHeap* _g1;
1206 public:
1207 ParRebuildRSTask(G1CollectedHeap* g1)
1208 : AbstractGangTask("ParRebuildRSTask"),
1209 _g1(g1)
1210 { }
1212 void work(uint worker_id) {
1213 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1214 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1215 _g1->workers()->active_workers(),
1216 HeapRegion::RebuildRSClaimValue);
1217 }
1218 };
1220 class PostCompactionPrinterClosure: public HeapRegionClosure {
1221 private:
1222 G1HRPrinter* _hr_printer;
1223 public:
1224 bool doHeapRegion(HeapRegion* hr) {
1225 assert(!hr->is_young(), "not expecting to find young regions");
1226 if (hr->is_free()) {
1227 // We only generate output for non-empty regions.
1228 } else if (hr->startsHumongous()) {
1229 if (hr->region_num() == 1) {
1230 // single humongous region
1231 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1232 } else {
1233 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1234 }
1235 } else if (hr->continuesHumongous()) {
1236 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1237 } else if (hr->is_old()) {
1238 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1239 } else {
1240 ShouldNotReachHere();
1241 }
1242 return false;
1243 }
1245 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1246 : _hr_printer(hr_printer) { }
1247 };
1249 void G1CollectedHeap::print_hrm_post_compaction() {
1250 PostCompactionPrinterClosure cl(hr_printer());
1251 heap_region_iterate(&cl);
1252 }
1254 bool G1CollectedHeap::do_collection(bool explicit_gc,
1255 bool clear_all_soft_refs,
1256 size_t word_size) {
1257 assert_at_safepoint(true /* should_be_vm_thread */);
1259 if (GC_locker::check_active_before_gc()) {
1260 return false;
1261 }
1263 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1264 gc_timer->register_gc_start();
1266 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1267 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1269 SvcGCMarker sgcm(SvcGCMarker::FULL);
1270 ResourceMark rm;
1272 print_heap_before_gc();
1273 trace_heap_before_gc(gc_tracer);
1275 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1277 verify_region_sets_optional();
1279 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1280 collector_policy()->should_clear_all_soft_refs();
1282 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1284 {
1285 IsGCActiveMark x;
1287 // Timing
1288 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1289 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1291 {
1292 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1293 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1294 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1296 double start = os::elapsedTime();
1297 g1_policy()->record_full_collection_start();
1299 // Note: When we have a more flexible GC logging framework that
1300 // allows us to add optional attributes to a GC log record we
1301 // could consider timing and reporting how long we wait in the
1302 // following two methods.
1303 wait_while_free_regions_coming();
1304 // If we start the compaction before the CM threads finish
1305 // scanning the root regions we might trip them over as we'll
1306 // be moving objects / updating references. So let's wait until
1307 // they are done. By telling them to abort, they should complete
1308 // early.
1309 _cm->root_regions()->abort();
1310 _cm->root_regions()->wait_until_scan_finished();
1311 append_secondary_free_list_if_not_empty_with_lock();
1313 gc_prologue(true);
1314 increment_total_collections(true /* full gc */);
1315 increment_old_marking_cycles_started();
1317 assert(used() == recalculate_used(), "Should be equal");
1319 verify_before_gc();
1321 check_bitmaps("Full GC Start");
1322 pre_full_gc_dump(gc_timer);
1324 COMPILER2_PRESENT(DerivedPointerTable::clear());
1326 // Disable discovery and empty the discovered lists
1327 // for the CM ref processor.
1328 ref_processor_cm()->disable_discovery();
1329 ref_processor_cm()->abandon_partial_discovery();
1330 ref_processor_cm()->verify_no_references_recorded();
1332 // Abandon current iterations of concurrent marking and concurrent
1333 // refinement, if any are in progress. We have to do this before
1334 // wait_until_scan_finished() below.
1335 concurrent_mark()->abort();
1337 // Make sure we'll choose a new allocation region afterwards.
1338 _allocator->release_mutator_alloc_region();
1339 _allocator->abandon_gc_alloc_regions();
1340 g1_rem_set()->cleanupHRRS();
1342 // We should call this after we retire any currently active alloc
1343 // regions so that all the ALLOC / RETIRE events are generated
1344 // before the start GC event.
1345 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1347 // We may have added regions to the current incremental collection
1348 // set between the last GC or pause and now. We need to clear the
1349 // incremental collection set and then start rebuilding it afresh
1350 // after this full GC.
1351 abandon_collection_set(g1_policy()->inc_cset_head());
1352 g1_policy()->clear_incremental_cset();
1353 g1_policy()->stop_incremental_cset_building();
1355 tear_down_region_sets(false /* free_list_only */);
1356 g1_policy()->set_gcs_are_young(true);
1358 // See the comments in g1CollectedHeap.hpp and
1359 // G1CollectedHeap::ref_processing_init() about
1360 // how reference processing currently works in G1.
1362 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1363 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1365 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1366 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1368 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1369 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1371 // Do collection work
1372 {
1373 HandleMark hm; // Discard invalid handles created during gc
1374 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1375 }
1377 assert(num_free_regions() == 0, "we should not have added any free regions");
1378 rebuild_region_sets(false /* free_list_only */);
1380 // Enqueue any discovered reference objects that have
1381 // not been removed from the discovered lists.
1382 ref_processor_stw()->enqueue_discovered_references();
1384 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1386 MemoryService::track_memory_usage();
1388 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1389 ref_processor_stw()->verify_no_references_recorded();
1391 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1392 ClassLoaderDataGraph::purge();
1393 MetaspaceAux::verify_metrics();
1395 // Note: since we've just done a full GC, concurrent
1396 // marking is no longer active. Therefore we need not
1397 // re-enable reference discovery for the CM ref processor.
1398 // That will be done at the start of the next marking cycle.
1399 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1400 ref_processor_cm()->verify_no_references_recorded();
1402 reset_gc_time_stamp();
1403 // Since everything potentially moved, we will clear all remembered
1404 // sets, and clear all cards. Later we will rebuild remembered
1405 // sets. We will also reset the GC time stamps of the regions.
1406 clear_rsets_post_compaction();
1407 check_gc_time_stamps();
1409 // Resize the heap if necessary.
1410 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1412 if (_hr_printer.is_active()) {
1413 // We should do this after we potentially resize the heap so
1414 // that all the COMMIT / UNCOMMIT events are generated before
1415 // the end GC event.
1417 print_hrm_post_compaction();
1418 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1419 }
1421 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1422 if (hot_card_cache->use_cache()) {
1423 hot_card_cache->reset_card_counts();
1424 hot_card_cache->reset_hot_cache();
1425 }
1427 // Rebuild remembered sets of all regions.
1428 if (G1CollectedHeap::use_parallel_gc_threads()) {
1429 uint n_workers =
1430 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1431 workers()->active_workers(),
1432 Threads::number_of_non_daemon_threads());
1433 assert(UseDynamicNumberOfGCThreads ||
1434 n_workers == workers()->total_workers(),
1435 "If not dynamic should be using all the workers");
1436 workers()->set_active_workers(n_workers);
1437 // Set parallel threads in the heap (_n_par_threads) only
1438 // before a parallel phase and always reset it to 0 after
1439 // the phase so that the number of parallel threads does
1440 // no get carried forward to a serial phase where there
1441 // may be code that is "possibly_parallel".
1442 set_par_threads(n_workers);
1444 ParRebuildRSTask rebuild_rs_task(this);
1445 assert(check_heap_region_claim_values(
1446 HeapRegion::InitialClaimValue), "sanity check");
1447 assert(UseDynamicNumberOfGCThreads ||
1448 workers()->active_workers() == workers()->total_workers(),
1449 "Unless dynamic should use total workers");
1450 // Use the most recent number of active workers
1451 assert(workers()->active_workers() > 0,
1452 "Active workers not properly set");
1453 set_par_threads(workers()->active_workers());
1454 workers()->run_task(&rebuild_rs_task);
1455 set_par_threads(0);
1456 assert(check_heap_region_claim_values(
1457 HeapRegion::RebuildRSClaimValue), "sanity check");
1458 reset_heap_region_claim_values();
1459 } else {
1460 RebuildRSOutOfRegionClosure rebuild_rs(this);
1461 heap_region_iterate(&rebuild_rs);
1462 }
1464 // Rebuild the strong code root lists for each region
1465 rebuild_strong_code_roots();
1467 if (true) { // FIXME
1468 MetaspaceGC::compute_new_size();
1469 }
1471 #ifdef TRACESPINNING
1472 ParallelTaskTerminator::print_termination_counts();
1473 #endif
1475 // Discard all rset updates
1476 JavaThread::dirty_card_queue_set().abandon_logs();
1477 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1479 _young_list->reset_sampled_info();
1480 // At this point there should be no regions in the
1481 // entire heap tagged as young.
1482 assert(check_young_list_empty(true /* check_heap */),
1483 "young list should be empty at this point");
1485 // Update the number of full collections that have been completed.
1486 increment_old_marking_cycles_completed(false /* concurrent */);
1488 _hrm.verify_optional();
1489 verify_region_sets_optional();
1491 verify_after_gc();
1493 // Clear the previous marking bitmap, if needed for bitmap verification.
1494 // Note we cannot do this when we clear the next marking bitmap in
1495 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1496 // objects marked during a full GC against the previous bitmap.
1497 // But we need to clear it before calling check_bitmaps below since
1498 // the full GC has compacted objects and updated TAMS but not updated
1499 // the prev bitmap.
1500 if (G1VerifyBitmaps) {
1501 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1502 }
1503 check_bitmaps("Full GC End");
1505 // Start a new incremental collection set for the next pause
1506 assert(g1_policy()->collection_set() == NULL, "must be");
1507 g1_policy()->start_incremental_cset_building();
1509 clear_cset_fast_test();
1511 _allocator->init_mutator_alloc_region();
1513 double end = os::elapsedTime();
1514 g1_policy()->record_full_collection_end();
1516 if (G1Log::fine()) {
1517 g1_policy()->print_heap_transition();
1518 }
1520 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1521 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1522 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1523 // before any GC notifications are raised.
1524 g1mm()->update_sizes();
1526 gc_epilogue(true);
1527 }
1529 if (G1Log::finer()) {
1530 g1_policy()->print_detailed_heap_transition(true /* full */);
1531 }
1533 print_heap_after_gc();
1534 trace_heap_after_gc(gc_tracer);
1536 post_full_gc_dump(gc_timer);
1538 gc_timer->register_gc_end();
1539 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1540 }
1542 return true;
1543 }
1545 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1546 // do_collection() will return whether it succeeded in performing
1547 // the GC. Currently, there is no facility on the
1548 // do_full_collection() API to notify the caller than the collection
1549 // did not succeed (e.g., because it was locked out by the GC
1550 // locker). So, right now, we'll ignore the return value.
1551 bool dummy = do_collection(true, /* explicit_gc */
1552 clear_all_soft_refs,
1553 0 /* word_size */);
1554 }
1556 // This code is mostly copied from TenuredGeneration.
1557 void
1558 G1CollectedHeap::
1559 resize_if_necessary_after_full_collection(size_t word_size) {
1560 // Include the current allocation, if any, and bytes that will be
1561 // pre-allocated to support collections, as "used".
1562 const size_t used_after_gc = used();
1563 const size_t capacity_after_gc = capacity();
1564 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1566 // This is enforced in arguments.cpp.
1567 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1568 "otherwise the code below doesn't make sense");
1570 // We don't have floating point command-line arguments
1571 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1572 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1573 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1574 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1576 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1577 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1579 // We have to be careful here as these two calculations can overflow
1580 // 32-bit size_t's.
1581 double used_after_gc_d = (double) used_after_gc;
1582 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1583 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1585 // Let's make sure that they are both under the max heap size, which
1586 // by default will make them fit into a size_t.
1587 double desired_capacity_upper_bound = (double) max_heap_size;
1588 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1589 desired_capacity_upper_bound);
1590 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1591 desired_capacity_upper_bound);
1593 // We can now safely turn them into size_t's.
1594 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1595 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1597 // This assert only makes sense here, before we adjust them
1598 // with respect to the min and max heap size.
1599 assert(minimum_desired_capacity <= maximum_desired_capacity,
1600 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1601 "maximum_desired_capacity = "SIZE_FORMAT,
1602 minimum_desired_capacity, maximum_desired_capacity));
1604 // Should not be greater than the heap max size. No need to adjust
1605 // it with respect to the heap min size as it's a lower bound (i.e.,
1606 // we'll try to make the capacity larger than it, not smaller).
1607 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1608 // Should not be less than the heap min size. No need to adjust it
1609 // with respect to the heap max size as it's an upper bound (i.e.,
1610 // we'll try to make the capacity smaller than it, not greater).
1611 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1613 if (capacity_after_gc < minimum_desired_capacity) {
1614 // Don't expand unless it's significant
1615 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1616 ergo_verbose4(ErgoHeapSizing,
1617 "attempt heap expansion",
1618 ergo_format_reason("capacity lower than "
1619 "min desired capacity after Full GC")
1620 ergo_format_byte("capacity")
1621 ergo_format_byte("occupancy")
1622 ergo_format_byte_perc("min desired capacity"),
1623 capacity_after_gc, used_after_gc,
1624 minimum_desired_capacity, (double) MinHeapFreeRatio);
1625 expand(expand_bytes);
1627 // No expansion, now see if we want to shrink
1628 } else if (capacity_after_gc > maximum_desired_capacity) {
1629 // Capacity too large, compute shrinking size
1630 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1631 ergo_verbose4(ErgoHeapSizing,
1632 "attempt heap shrinking",
1633 ergo_format_reason("capacity higher than "
1634 "max desired capacity after Full GC")
1635 ergo_format_byte("capacity")
1636 ergo_format_byte("occupancy")
1637 ergo_format_byte_perc("max desired capacity"),
1638 capacity_after_gc, used_after_gc,
1639 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1640 shrink(shrink_bytes);
1641 }
1642 }
1645 HeapWord*
1646 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1647 AllocationContext_t context,
1648 bool* succeeded) {
1649 assert_at_safepoint(true /* should_be_vm_thread */);
1651 *succeeded = true;
1652 // Let's attempt the allocation first.
1653 HeapWord* result =
1654 attempt_allocation_at_safepoint(word_size,
1655 context,
1656 false /* expect_null_mutator_alloc_region */);
1657 if (result != NULL) {
1658 assert(*succeeded, "sanity");
1659 return result;
1660 }
1662 // In a G1 heap, we're supposed to keep allocation from failing by
1663 // incremental pauses. Therefore, at least for now, we'll favor
1664 // expansion over collection. (This might change in the future if we can
1665 // do something smarter than full collection to satisfy a failed alloc.)
1666 result = expand_and_allocate(word_size, context);
1667 if (result != NULL) {
1668 assert(*succeeded, "sanity");
1669 return result;
1670 }
1672 // Expansion didn't work, we'll try to do a Full GC.
1673 bool gc_succeeded = do_collection(false, /* explicit_gc */
1674 false, /* clear_all_soft_refs */
1675 word_size);
1676 if (!gc_succeeded) {
1677 *succeeded = false;
1678 return NULL;
1679 }
1681 // Retry the allocation
1682 result = attempt_allocation_at_safepoint(word_size,
1683 context,
1684 true /* expect_null_mutator_alloc_region */);
1685 if (result != NULL) {
1686 assert(*succeeded, "sanity");
1687 return result;
1688 }
1690 // Then, try a Full GC that will collect all soft references.
1691 gc_succeeded = do_collection(false, /* explicit_gc */
1692 true, /* clear_all_soft_refs */
1693 word_size);
1694 if (!gc_succeeded) {
1695 *succeeded = false;
1696 return NULL;
1697 }
1699 // Retry the allocation once more
1700 result = attempt_allocation_at_safepoint(word_size,
1701 context,
1702 true /* expect_null_mutator_alloc_region */);
1703 if (result != NULL) {
1704 assert(*succeeded, "sanity");
1705 return result;
1706 }
1708 assert(!collector_policy()->should_clear_all_soft_refs(),
1709 "Flag should have been handled and cleared prior to this point");
1711 // What else? We might try synchronous finalization later. If the total
1712 // space available is large enough for the allocation, then a more
1713 // complete compaction phase than we've tried so far might be
1714 // appropriate.
1715 assert(*succeeded, "sanity");
1716 return NULL;
1717 }
1719 // Attempting to expand the heap sufficiently
1720 // to support an allocation of the given "word_size". If
1721 // successful, perform the allocation and return the address of the
1722 // allocated block, or else "NULL".
1724 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1725 assert_at_safepoint(true /* should_be_vm_thread */);
1727 verify_region_sets_optional();
1729 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1730 ergo_verbose1(ErgoHeapSizing,
1731 "attempt heap expansion",
1732 ergo_format_reason("allocation request failed")
1733 ergo_format_byte("allocation request"),
1734 word_size * HeapWordSize);
1735 if (expand(expand_bytes)) {
1736 _hrm.verify_optional();
1737 verify_region_sets_optional();
1738 return attempt_allocation_at_safepoint(word_size,
1739 context,
1740 false /* expect_null_mutator_alloc_region */);
1741 }
1742 return NULL;
1743 }
1745 bool G1CollectedHeap::expand(size_t expand_bytes) {
1746 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1747 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1748 HeapRegion::GrainBytes);
1749 ergo_verbose2(ErgoHeapSizing,
1750 "expand the heap",
1751 ergo_format_byte("requested expansion amount")
1752 ergo_format_byte("attempted expansion amount"),
1753 expand_bytes, aligned_expand_bytes);
1755 if (is_maximal_no_gc()) {
1756 ergo_verbose0(ErgoHeapSizing,
1757 "did not expand the heap",
1758 ergo_format_reason("heap already fully expanded"));
1759 return false;
1760 }
1762 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1763 assert(regions_to_expand > 0, "Must expand by at least one region");
1765 uint expanded_by = _hrm.expand_by(regions_to_expand);
1767 if (expanded_by > 0) {
1768 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1769 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1770 g1_policy()->record_new_heap_size(num_regions());
1771 } else {
1772 ergo_verbose0(ErgoHeapSizing,
1773 "did not expand the heap",
1774 ergo_format_reason("heap expansion operation failed"));
1775 // The expansion of the virtual storage space was unsuccessful.
1776 // Let's see if it was because we ran out of swap.
1777 if (G1ExitOnExpansionFailure &&
1778 _hrm.available() >= regions_to_expand) {
1779 // We had head room...
1780 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1781 }
1782 }
1783 return regions_to_expand > 0;
1784 }
1786 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1787 size_t aligned_shrink_bytes =
1788 ReservedSpace::page_align_size_down(shrink_bytes);
1789 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1790 HeapRegion::GrainBytes);
1791 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1793 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1794 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1796 ergo_verbose3(ErgoHeapSizing,
1797 "shrink the heap",
1798 ergo_format_byte("requested shrinking amount")
1799 ergo_format_byte("aligned shrinking amount")
1800 ergo_format_byte("attempted shrinking amount"),
1801 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1802 if (num_regions_removed > 0) {
1803 g1_policy()->record_new_heap_size(num_regions());
1804 } else {
1805 ergo_verbose0(ErgoHeapSizing,
1806 "did not shrink the heap",
1807 ergo_format_reason("heap shrinking operation failed"));
1808 }
1809 }
1811 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1812 verify_region_sets_optional();
1814 // We should only reach here at the end of a Full GC which means we
1815 // should not not be holding to any GC alloc regions. The method
1816 // below will make sure of that and do any remaining clean up.
1817 _allocator->abandon_gc_alloc_regions();
1819 // Instead of tearing down / rebuilding the free lists here, we
1820 // could instead use the remove_all_pending() method on free_list to
1821 // remove only the ones that we need to remove.
1822 tear_down_region_sets(true /* free_list_only */);
1823 shrink_helper(shrink_bytes);
1824 rebuild_region_sets(true /* free_list_only */);
1826 _hrm.verify_optional();
1827 verify_region_sets_optional();
1828 }
1830 // Public methods.
1832 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1833 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1834 #endif // _MSC_VER
1837 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1838 SharedHeap(policy_),
1839 _g1_policy(policy_),
1840 _dirty_card_queue_set(false),
1841 _into_cset_dirty_card_queue_set(false),
1842 _is_alive_closure_cm(this),
1843 _is_alive_closure_stw(this),
1844 _ref_processor_cm(NULL),
1845 _ref_processor_stw(NULL),
1846 _bot_shared(NULL),
1847 _evac_failure_scan_stack(NULL),
1848 _mark_in_progress(false),
1849 _cg1r(NULL),
1850 _g1mm(NULL),
1851 _refine_cte_cl(NULL),
1852 _full_collection(false),
1853 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1854 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1855 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1856 _humongous_is_live(),
1857 _has_humongous_reclaim_candidates(false),
1858 _free_regions_coming(false),
1859 _young_list(new YoungList(this)),
1860 _gc_time_stamp(0),
1861 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1862 _old_plab_stats(OldPLABSize, PLABWeight),
1863 _expand_heap_after_alloc_failure(true),
1864 _surviving_young_words(NULL),
1865 _old_marking_cycles_started(0),
1866 _old_marking_cycles_completed(0),
1867 _concurrent_cycle_started(false),
1868 _heap_summary_sent(false),
1869 _in_cset_fast_test(),
1870 _dirty_cards_region_list(NULL),
1871 _worker_cset_start_region(NULL),
1872 _worker_cset_start_region_time_stamp(NULL),
1873 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1874 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1875 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1876 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1878 _g1h = this;
1880 _allocator = G1Allocator::create_allocator(_g1h);
1881 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1883 int n_queues = MAX2((int)ParallelGCThreads, 1);
1884 _task_queues = new RefToScanQueueSet(n_queues);
1886 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1887 assert(n_rem_sets > 0, "Invariant.");
1889 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1890 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1891 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1893 for (int i = 0; i < n_queues; i++) {
1894 RefToScanQueue* q = new RefToScanQueue();
1895 q->initialize();
1896 _task_queues->register_queue(i, q);
1897 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1898 }
1899 clear_cset_start_regions();
1901 // Initialize the G1EvacuationFailureALot counters and flags.
1902 NOT_PRODUCT(reset_evacuation_should_fail();)
1904 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1905 }
1907 jint G1CollectedHeap::initialize() {
1908 CollectedHeap::pre_initialize();
1909 os::enable_vtime();
1911 G1Log::init();
1913 // Necessary to satisfy locking discipline assertions.
1915 MutexLocker x(Heap_lock);
1917 // We have to initialize the printer before committing the heap, as
1918 // it will be used then.
1919 _hr_printer.set_active(G1PrintHeapRegions);
1921 // While there are no constraints in the GC code that HeapWordSize
1922 // be any particular value, there are multiple other areas in the
1923 // system which believe this to be true (e.g. oop->object_size in some
1924 // cases incorrectly returns the size in wordSize units rather than
1925 // HeapWordSize).
1926 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1928 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1929 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1930 size_t heap_alignment = collector_policy()->heap_alignment();
1932 // Ensure that the sizes are properly aligned.
1933 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1934 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1935 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1937 _refine_cte_cl = new RefineCardTableEntryClosure();
1939 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1941 // Reserve the maximum.
1943 // When compressed oops are enabled, the preferred heap base
1944 // is calculated by subtracting the requested size from the
1945 // 32Gb boundary and using the result as the base address for
1946 // heap reservation. If the requested size is not aligned to
1947 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1948 // into the ReservedHeapSpace constructor) then the actual
1949 // base of the reserved heap may end up differing from the
1950 // address that was requested (i.e. the preferred heap base).
1951 // If this happens then we could end up using a non-optimal
1952 // compressed oops mode.
1954 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1955 heap_alignment);
1957 // It is important to do this in a way such that concurrent readers can't
1958 // temporarily think something is in the heap. (I've actually seen this
1959 // happen in asserts: DLD.)
1960 _reserved.set_word_size(0);
1961 _reserved.set_start((HeapWord*)heap_rs.base());
1962 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1964 // Create the gen rem set (and barrier set) for the entire reserved region.
1965 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1966 set_barrier_set(rem_set()->bs());
1967 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1968 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1969 return JNI_ENOMEM;
1970 }
1972 // Also create a G1 rem set.
1973 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1975 // Carve out the G1 part of the heap.
1977 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1978 G1RegionToSpaceMapper* heap_storage =
1979 G1RegionToSpaceMapper::create_mapper(g1_rs,
1980 UseLargePages ? os::large_page_size() : os::vm_page_size(),
1981 HeapRegion::GrainBytes,
1982 1,
1983 mtJavaHeap);
1984 heap_storage->set_mapping_changed_listener(&_listener);
1986 // Reserve space for the block offset table. We do not support automatic uncommit
1987 // for the card table at this time. BOT only.
1988 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1989 G1RegionToSpaceMapper* bot_storage =
1990 G1RegionToSpaceMapper::create_mapper(bot_rs,
1991 os::vm_page_size(),
1992 HeapRegion::GrainBytes,
1993 G1BlockOffsetSharedArray::N_bytes,
1994 mtGC);
1996 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1997 G1RegionToSpaceMapper* cardtable_storage =
1998 G1RegionToSpaceMapper::create_mapper(cardtable_rs,
1999 os::vm_page_size(),
2000 HeapRegion::GrainBytes,
2001 G1BlockOffsetSharedArray::N_bytes,
2002 mtGC);
2004 // Reserve space for the card counts table.
2005 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2006 G1RegionToSpaceMapper* card_counts_storage =
2007 G1RegionToSpaceMapper::create_mapper(card_counts_rs,
2008 os::vm_page_size(),
2009 HeapRegion::GrainBytes,
2010 G1BlockOffsetSharedArray::N_bytes,
2011 mtGC);
2013 // Reserve space for prev and next bitmap.
2014 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2016 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2017 G1RegionToSpaceMapper* prev_bitmap_storage =
2018 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
2019 os::vm_page_size(),
2020 HeapRegion::GrainBytes,
2021 CMBitMap::mark_distance(),
2022 mtGC);
2024 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2025 G1RegionToSpaceMapper* next_bitmap_storage =
2026 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
2027 os::vm_page_size(),
2028 HeapRegion::GrainBytes,
2029 CMBitMap::mark_distance(),
2030 mtGC);
2032 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2033 g1_barrier_set()->initialize(cardtable_storage);
2034 // Do later initialization work for concurrent refinement.
2035 _cg1r->init(card_counts_storage);
2037 // 6843694 - ensure that the maximum region index can fit
2038 // in the remembered set structures.
2039 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2040 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2042 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2043 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2044 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2045 "too many cards per region");
2047 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2049 _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage);
2051 _g1h = this;
2053 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2054 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2056 // Create the ConcurrentMark data structure and thread.
2057 // (Must do this late, so that "max_regions" is defined.)
2058 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2059 if (_cm == NULL || !_cm->completed_initialization()) {
2060 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2061 return JNI_ENOMEM;
2062 }
2063 _cmThread = _cm->cmThread();
2065 // Initialize the from_card cache structure of HeapRegionRemSet.
2066 HeapRegionRemSet::init_heap(max_regions());
2068 // Now expand into the initial heap size.
2069 if (!expand(init_byte_size)) {
2070 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2071 return JNI_ENOMEM;
2072 }
2074 // Perform any initialization actions delegated to the policy.
2075 g1_policy()->init();
2077 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2078 SATB_Q_FL_lock,
2079 G1SATBProcessCompletedThreshold,
2080 Shared_SATB_Q_lock);
2082 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2083 DirtyCardQ_CBL_mon,
2084 DirtyCardQ_FL_lock,
2085 concurrent_g1_refine()->yellow_zone(),
2086 concurrent_g1_refine()->red_zone(),
2087 Shared_DirtyCardQ_lock);
2089 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2090 DirtyCardQ_CBL_mon,
2091 DirtyCardQ_FL_lock,
2092 -1, // never trigger processing
2093 -1, // no limit on length
2094 Shared_DirtyCardQ_lock,
2095 &JavaThread::dirty_card_queue_set());
2097 // Initialize the card queue set used to hold cards containing
2098 // references into the collection set.
2099 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2100 DirtyCardQ_CBL_mon,
2101 DirtyCardQ_FL_lock,
2102 -1, // never trigger processing
2103 -1, // no limit on length
2104 Shared_DirtyCardQ_lock,
2105 &JavaThread::dirty_card_queue_set());
2107 // In case we're keeping closure specialization stats, initialize those
2108 // counts and that mechanism.
2109 SpecializationStats::clear();
2111 // Here we allocate the dummy HeapRegion that is required by the
2112 // G1AllocRegion class.
2113 HeapRegion* dummy_region = _hrm.get_dummy_region();
2115 // We'll re-use the same region whether the alloc region will
2116 // require BOT updates or not and, if it doesn't, then a non-young
2117 // region will complain that it cannot support allocations without
2118 // BOT updates. So we'll tag the dummy region as eden to avoid that.
2119 dummy_region->set_eden();
2120 // Make sure it's full.
2121 dummy_region->set_top(dummy_region->end());
2122 G1AllocRegion::setup(this, dummy_region);
2124 _allocator->init_mutator_alloc_region();
2126 // Do create of the monitoring and management support so that
2127 // values in the heap have been properly initialized.
2128 _g1mm = new G1MonitoringSupport(this);
2130 G1StringDedup::initialize();
2132 return JNI_OK;
2133 }
2135 void G1CollectedHeap::stop() {
2136 // Stop all concurrent threads. We do this to make sure these threads
2137 // do not continue to execute and access resources (e.g. gclog_or_tty)
2138 // that are destroyed during shutdown.
2139 _cg1r->stop();
2140 _cmThread->stop();
2141 if (G1StringDedup::is_enabled()) {
2142 G1StringDedup::stop();
2143 }
2144 }
2146 void G1CollectedHeap::clear_humongous_is_live_table() {
2147 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2148 _humongous_is_live.clear();
2149 }
2151 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2152 return HeapRegion::max_region_size();
2153 }
2155 void G1CollectedHeap::ref_processing_init() {
2156 // Reference processing in G1 currently works as follows:
2157 //
2158 // * There are two reference processor instances. One is
2159 // used to record and process discovered references
2160 // during concurrent marking; the other is used to
2161 // record and process references during STW pauses
2162 // (both full and incremental).
2163 // * Both ref processors need to 'span' the entire heap as
2164 // the regions in the collection set may be dotted around.
2165 //
2166 // * For the concurrent marking ref processor:
2167 // * Reference discovery is enabled at initial marking.
2168 // * Reference discovery is disabled and the discovered
2169 // references processed etc during remarking.
2170 // * Reference discovery is MT (see below).
2171 // * Reference discovery requires a barrier (see below).
2172 // * Reference processing may or may not be MT
2173 // (depending on the value of ParallelRefProcEnabled
2174 // and ParallelGCThreads).
2175 // * A full GC disables reference discovery by the CM
2176 // ref processor and abandons any entries on it's
2177 // discovered lists.
2178 //
2179 // * For the STW processor:
2180 // * Non MT discovery is enabled at the start of a full GC.
2181 // * Processing and enqueueing during a full GC is non-MT.
2182 // * During a full GC, references are processed after marking.
2183 //
2184 // * Discovery (may or may not be MT) is enabled at the start
2185 // of an incremental evacuation pause.
2186 // * References are processed near the end of a STW evacuation pause.
2187 // * For both types of GC:
2188 // * Discovery is atomic - i.e. not concurrent.
2189 // * Reference discovery will not need a barrier.
2191 SharedHeap::ref_processing_init();
2192 MemRegion mr = reserved_region();
2194 // Concurrent Mark ref processor
2195 _ref_processor_cm =
2196 new ReferenceProcessor(mr, // span
2197 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2198 // mt processing
2199 (int) ParallelGCThreads,
2200 // degree of mt processing
2201 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2202 // mt discovery
2203 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2204 // degree of mt discovery
2205 false,
2206 // Reference discovery is not atomic
2207 &_is_alive_closure_cm);
2208 // is alive closure
2209 // (for efficiency/performance)
2211 // STW ref processor
2212 _ref_processor_stw =
2213 new ReferenceProcessor(mr, // span
2214 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2215 // mt processing
2216 MAX2((int)ParallelGCThreads, 1),
2217 // degree of mt processing
2218 (ParallelGCThreads > 1),
2219 // mt discovery
2220 MAX2((int)ParallelGCThreads, 1),
2221 // degree of mt discovery
2222 true,
2223 // Reference discovery is atomic
2224 &_is_alive_closure_stw);
2225 // is alive closure
2226 // (for efficiency/performance)
2227 }
2229 size_t G1CollectedHeap::capacity() const {
2230 return _hrm.length() * HeapRegion::GrainBytes;
2231 }
2233 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2234 assert(!hr->continuesHumongous(), "pre-condition");
2235 hr->reset_gc_time_stamp();
2236 if (hr->startsHumongous()) {
2237 uint first_index = hr->hrm_index() + 1;
2238 uint last_index = hr->last_hc_index();
2239 for (uint i = first_index; i < last_index; i += 1) {
2240 HeapRegion* chr = region_at(i);
2241 assert(chr->continuesHumongous(), "sanity");
2242 chr->reset_gc_time_stamp();
2243 }
2244 }
2245 }
2247 #ifndef PRODUCT
2248 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2249 private:
2250 unsigned _gc_time_stamp;
2251 bool _failures;
2253 public:
2254 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2255 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2257 virtual bool doHeapRegion(HeapRegion* hr) {
2258 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2259 if (_gc_time_stamp != region_gc_time_stamp) {
2260 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2261 "expected %d", HR_FORMAT_PARAMS(hr),
2262 region_gc_time_stamp, _gc_time_stamp);
2263 _failures = true;
2264 }
2265 return false;
2266 }
2268 bool failures() { return _failures; }
2269 };
2271 void G1CollectedHeap::check_gc_time_stamps() {
2272 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2273 heap_region_iterate(&cl);
2274 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2275 }
2276 #endif // PRODUCT
2278 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2279 DirtyCardQueue* into_cset_dcq,
2280 bool concurrent,
2281 uint worker_i) {
2282 // Clean cards in the hot card cache
2283 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2284 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2286 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2287 size_t n_completed_buffers = 0;
2288 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2289 n_completed_buffers++;
2290 }
2291 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2292 dcqs.clear_n_completed_buffers();
2293 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2294 }
2297 // Computes the sum of the storage used by the various regions.
2298 size_t G1CollectedHeap::used() const {
2299 return _allocator->used();
2300 }
2302 size_t G1CollectedHeap::used_unlocked() const {
2303 return _allocator->used_unlocked();
2304 }
2306 class SumUsedClosure: public HeapRegionClosure {
2307 size_t _used;
2308 public:
2309 SumUsedClosure() : _used(0) {}
2310 bool doHeapRegion(HeapRegion* r) {
2311 if (!r->continuesHumongous()) {
2312 _used += r->used();
2313 }
2314 return false;
2315 }
2316 size_t result() { return _used; }
2317 };
2319 size_t G1CollectedHeap::recalculate_used() const {
2320 double recalculate_used_start = os::elapsedTime();
2322 SumUsedClosure blk;
2323 heap_region_iterate(&blk);
2325 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2326 return blk.result();
2327 }
2329 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2330 switch (cause) {
2331 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2332 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2333 case GCCause::_g1_humongous_allocation: return true;
2334 case GCCause::_update_allocation_context_stats_inc: return true;
2335 default: return false;
2336 }
2337 }
2339 #ifndef PRODUCT
2340 void G1CollectedHeap::allocate_dummy_regions() {
2341 // Let's fill up most of the region
2342 size_t word_size = HeapRegion::GrainWords - 1024;
2343 // And as a result the region we'll allocate will be humongous.
2344 guarantee(isHumongous(word_size), "sanity");
2346 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2347 // Let's use the existing mechanism for the allocation
2348 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2349 AllocationContext::system());
2350 if (dummy_obj != NULL) {
2351 MemRegion mr(dummy_obj, word_size);
2352 CollectedHeap::fill_with_object(mr);
2353 } else {
2354 // If we can't allocate once, we probably cannot allocate
2355 // again. Let's get out of the loop.
2356 break;
2357 }
2358 }
2359 }
2360 #endif // !PRODUCT
2362 void G1CollectedHeap::increment_old_marking_cycles_started() {
2363 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2364 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2365 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2366 _old_marking_cycles_started, _old_marking_cycles_completed));
2368 _old_marking_cycles_started++;
2369 }
2371 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2372 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2374 // We assume that if concurrent == true, then the caller is a
2375 // concurrent thread that was joined the Suspendible Thread
2376 // Set. If there's ever a cheap way to check this, we should add an
2377 // assert here.
2379 // Given that this method is called at the end of a Full GC or of a
2380 // concurrent cycle, and those can be nested (i.e., a Full GC can
2381 // interrupt a concurrent cycle), the number of full collections
2382 // completed should be either one (in the case where there was no
2383 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2384 // behind the number of full collections started.
2386 // This is the case for the inner caller, i.e. a Full GC.
2387 assert(concurrent ||
2388 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2389 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2390 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2391 "is inconsistent with _old_marking_cycles_completed = %u",
2392 _old_marking_cycles_started, _old_marking_cycles_completed));
2394 // This is the case for the outer caller, i.e. the concurrent cycle.
2395 assert(!concurrent ||
2396 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2397 err_msg("for outer caller (concurrent cycle): "
2398 "_old_marking_cycles_started = %u "
2399 "is inconsistent with _old_marking_cycles_completed = %u",
2400 _old_marking_cycles_started, _old_marking_cycles_completed));
2402 _old_marking_cycles_completed += 1;
2404 // We need to clear the "in_progress" flag in the CM thread before
2405 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2406 // is set) so that if a waiter requests another System.gc() it doesn't
2407 // incorrectly see that a marking cycle is still in progress.
2408 if (concurrent) {
2409 _cmThread->clear_in_progress();
2410 }
2412 // This notify_all() will ensure that a thread that called
2413 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2414 // and it's waiting for a full GC to finish will be woken up. It is
2415 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2416 FullGCCount_lock->notify_all();
2417 }
2419 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2420 _concurrent_cycle_started = true;
2421 _gc_timer_cm->register_gc_start(start_time);
2423 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2424 trace_heap_before_gc(_gc_tracer_cm);
2425 }
2427 void G1CollectedHeap::register_concurrent_cycle_end() {
2428 if (_concurrent_cycle_started) {
2429 if (_cm->has_aborted()) {
2430 _gc_tracer_cm->report_concurrent_mode_failure();
2431 }
2433 _gc_timer_cm->register_gc_end();
2434 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2436 // Clear state variables to prepare for the next concurrent cycle.
2437 _concurrent_cycle_started = false;
2438 _heap_summary_sent = false;
2439 }
2440 }
2442 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2443 if (_concurrent_cycle_started) {
2444 // This function can be called when:
2445 // the cleanup pause is run
2446 // the concurrent cycle is aborted before the cleanup pause.
2447 // the concurrent cycle is aborted after the cleanup pause,
2448 // but before the concurrent cycle end has been registered.
2449 // Make sure that we only send the heap information once.
2450 if (!_heap_summary_sent) {
2451 trace_heap_after_gc(_gc_tracer_cm);
2452 _heap_summary_sent = true;
2453 }
2454 }
2455 }
2457 G1YCType G1CollectedHeap::yc_type() {
2458 bool is_young = g1_policy()->gcs_are_young();
2459 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2460 bool is_during_mark = mark_in_progress();
2462 if (is_initial_mark) {
2463 return InitialMark;
2464 } else if (is_during_mark) {
2465 return DuringMark;
2466 } else if (is_young) {
2467 return Normal;
2468 } else {
2469 return Mixed;
2470 }
2471 }
2473 void G1CollectedHeap::collect(GCCause::Cause cause) {
2474 assert_heap_not_locked();
2476 unsigned int gc_count_before;
2477 unsigned int old_marking_count_before;
2478 unsigned int full_gc_count_before;
2479 bool retry_gc;
2481 do {
2482 retry_gc = false;
2484 {
2485 MutexLocker ml(Heap_lock);
2487 // Read the GC count while holding the Heap_lock
2488 gc_count_before = total_collections();
2489 full_gc_count_before = total_full_collections();
2490 old_marking_count_before = _old_marking_cycles_started;
2491 }
2493 if (should_do_concurrent_full_gc(cause)) {
2494 // Schedule an initial-mark evacuation pause that will start a
2495 // concurrent cycle. We're setting word_size to 0 which means that
2496 // we are not requesting a post-GC allocation.
2497 VM_G1IncCollectionPause op(gc_count_before,
2498 0, /* word_size */
2499 true, /* should_initiate_conc_mark */
2500 g1_policy()->max_pause_time_ms(),
2501 cause);
2502 op.set_allocation_context(AllocationContext::current());
2504 VMThread::execute(&op);
2505 if (!op.pause_succeeded()) {
2506 if (old_marking_count_before == _old_marking_cycles_started) {
2507 retry_gc = op.should_retry_gc();
2508 } else {
2509 // A Full GC happened while we were trying to schedule the
2510 // initial-mark GC. No point in starting a new cycle given
2511 // that the whole heap was collected anyway.
2512 }
2514 if (retry_gc) {
2515 if (GC_locker::is_active_and_needs_gc()) {
2516 GC_locker::stall_until_clear();
2517 }
2518 }
2519 }
2520 } else {
2521 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2522 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2524 // Schedule a standard evacuation pause. We're setting word_size
2525 // to 0 which means that we are not requesting a post-GC allocation.
2526 VM_G1IncCollectionPause op(gc_count_before,
2527 0, /* word_size */
2528 false, /* should_initiate_conc_mark */
2529 g1_policy()->max_pause_time_ms(),
2530 cause);
2531 VMThread::execute(&op);
2532 } else {
2533 // Schedule a Full GC.
2534 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2535 VMThread::execute(&op);
2536 }
2537 }
2538 } while (retry_gc);
2539 }
2541 bool G1CollectedHeap::is_in(const void* p) const {
2542 if (_hrm.reserved().contains(p)) {
2543 // Given that we know that p is in the reserved space,
2544 // heap_region_containing_raw() should successfully
2545 // return the containing region.
2546 HeapRegion* hr = heap_region_containing_raw(p);
2547 return hr->is_in(p);
2548 } else {
2549 return false;
2550 }
2551 }
2553 #ifdef ASSERT
2554 bool G1CollectedHeap::is_in_exact(const void* p) const {
2555 bool contains = reserved_region().contains(p);
2556 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2557 if (contains && available) {
2558 return true;
2559 } else {
2560 return false;
2561 }
2562 }
2563 #endif
2565 // Iteration functions.
2567 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2569 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2570 ExtendedOopClosure* _cl;
2571 public:
2572 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2573 bool doHeapRegion(HeapRegion* r) {
2574 if (!r->continuesHumongous()) {
2575 r->oop_iterate(_cl);
2576 }
2577 return false;
2578 }
2579 };
2581 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2582 IterateOopClosureRegionClosure blk(cl);
2583 heap_region_iterate(&blk);
2584 }
2586 // Iterates an ObjectClosure over all objects within a HeapRegion.
2588 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2589 ObjectClosure* _cl;
2590 public:
2591 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2592 bool doHeapRegion(HeapRegion* r) {
2593 if (! r->continuesHumongous()) {
2594 r->object_iterate(_cl);
2595 }
2596 return false;
2597 }
2598 };
2600 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2601 IterateObjectClosureRegionClosure blk(cl);
2602 heap_region_iterate(&blk);
2603 }
2605 // Calls a SpaceClosure on a HeapRegion.
2607 class SpaceClosureRegionClosure: public HeapRegionClosure {
2608 SpaceClosure* _cl;
2609 public:
2610 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2611 bool doHeapRegion(HeapRegion* r) {
2612 _cl->do_space(r);
2613 return false;
2614 }
2615 };
2617 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2618 SpaceClosureRegionClosure blk(cl);
2619 heap_region_iterate(&blk);
2620 }
2622 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2623 _hrm.iterate(cl);
2624 }
2626 void
2627 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2628 uint worker_id,
2629 uint num_workers,
2630 jint claim_value) const {
2631 _hrm.par_iterate(cl, worker_id, num_workers, claim_value);
2632 }
2634 class ResetClaimValuesClosure: public HeapRegionClosure {
2635 public:
2636 bool doHeapRegion(HeapRegion* r) {
2637 r->set_claim_value(HeapRegion::InitialClaimValue);
2638 return false;
2639 }
2640 };
2642 void G1CollectedHeap::reset_heap_region_claim_values() {
2643 ResetClaimValuesClosure blk;
2644 heap_region_iterate(&blk);
2645 }
2647 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2648 ResetClaimValuesClosure blk;
2649 collection_set_iterate(&blk);
2650 }
2652 #ifdef ASSERT
2653 // This checks whether all regions in the heap have the correct claim
2654 // value. I also piggy-backed on this a check to ensure that the
2655 // humongous_start_region() information on "continues humongous"
2656 // regions is correct.
2658 class CheckClaimValuesClosure : public HeapRegionClosure {
2659 private:
2660 jint _claim_value;
2661 uint _failures;
2662 HeapRegion* _sh_region;
2664 public:
2665 CheckClaimValuesClosure(jint claim_value) :
2666 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2667 bool doHeapRegion(HeapRegion* r) {
2668 if (r->claim_value() != _claim_value) {
2669 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2670 "claim value = %d, should be %d",
2671 HR_FORMAT_PARAMS(r),
2672 r->claim_value(), _claim_value);
2673 ++_failures;
2674 }
2675 if (!r->isHumongous()) {
2676 _sh_region = NULL;
2677 } else if (r->startsHumongous()) {
2678 _sh_region = r;
2679 } else if (r->continuesHumongous()) {
2680 if (r->humongous_start_region() != _sh_region) {
2681 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2682 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2683 HR_FORMAT_PARAMS(r),
2684 r->humongous_start_region(),
2685 _sh_region);
2686 ++_failures;
2687 }
2688 }
2689 return false;
2690 }
2691 uint failures() { return _failures; }
2692 };
2694 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2695 CheckClaimValuesClosure cl(claim_value);
2696 heap_region_iterate(&cl);
2697 return cl.failures() == 0;
2698 }
2700 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2701 private:
2702 jint _claim_value;
2703 uint _failures;
2705 public:
2706 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2707 _claim_value(claim_value), _failures(0) { }
2709 uint failures() { return _failures; }
2711 bool doHeapRegion(HeapRegion* hr) {
2712 assert(hr->in_collection_set(), "how?");
2713 assert(!hr->isHumongous(), "H-region in CSet");
2714 if (hr->claim_value() != _claim_value) {
2715 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2716 "claim value = %d, should be %d",
2717 HR_FORMAT_PARAMS(hr),
2718 hr->claim_value(), _claim_value);
2719 _failures += 1;
2720 }
2721 return false;
2722 }
2723 };
2725 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2726 CheckClaimValuesInCSetHRClosure cl(claim_value);
2727 collection_set_iterate(&cl);
2728 return cl.failures() == 0;
2729 }
2730 #endif // ASSERT
2732 // Clear the cached CSet starting regions and (more importantly)
2733 // the time stamps. Called when we reset the GC time stamp.
2734 void G1CollectedHeap::clear_cset_start_regions() {
2735 assert(_worker_cset_start_region != NULL, "sanity");
2736 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2738 int n_queues = MAX2((int)ParallelGCThreads, 1);
2739 for (int i = 0; i < n_queues; i++) {
2740 _worker_cset_start_region[i] = NULL;
2741 _worker_cset_start_region_time_stamp[i] = 0;
2742 }
2743 }
2745 // Given the id of a worker, obtain or calculate a suitable
2746 // starting region for iterating over the current collection set.
2747 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2748 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2750 HeapRegion* result = NULL;
2751 unsigned gc_time_stamp = get_gc_time_stamp();
2753 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2754 // Cached starting region for current worker was set
2755 // during the current pause - so it's valid.
2756 // Note: the cached starting heap region may be NULL
2757 // (when the collection set is empty).
2758 result = _worker_cset_start_region[worker_i];
2759 assert(result == NULL || result->in_collection_set(), "sanity");
2760 return result;
2761 }
2763 // The cached entry was not valid so let's calculate
2764 // a suitable starting heap region for this worker.
2766 // We want the parallel threads to start their collection
2767 // set iteration at different collection set regions to
2768 // avoid contention.
2769 // If we have:
2770 // n collection set regions
2771 // p threads
2772 // Then thread t will start at region floor ((t * n) / p)
2774 result = g1_policy()->collection_set();
2775 if (G1CollectedHeap::use_parallel_gc_threads()) {
2776 uint cs_size = g1_policy()->cset_region_length();
2777 uint active_workers = workers()->active_workers();
2778 assert(UseDynamicNumberOfGCThreads ||
2779 active_workers == workers()->total_workers(),
2780 "Unless dynamic should use total workers");
2782 uint end_ind = (cs_size * worker_i) / active_workers;
2783 uint start_ind = 0;
2785 if (worker_i > 0 &&
2786 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2787 // Previous workers starting region is valid
2788 // so let's iterate from there
2789 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2790 result = _worker_cset_start_region[worker_i - 1];
2791 }
2793 for (uint i = start_ind; i < end_ind; i++) {
2794 result = result->next_in_collection_set();
2795 }
2796 }
2798 // Note: the calculated starting heap region may be NULL
2799 // (when the collection set is empty).
2800 assert(result == NULL || result->in_collection_set(), "sanity");
2801 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2802 "should be updated only once per pause");
2803 _worker_cset_start_region[worker_i] = result;
2804 OrderAccess::storestore();
2805 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2806 return result;
2807 }
2809 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2810 HeapRegion* r = g1_policy()->collection_set();
2811 while (r != NULL) {
2812 HeapRegion* next = r->next_in_collection_set();
2813 if (cl->doHeapRegion(r)) {
2814 cl->incomplete();
2815 return;
2816 }
2817 r = next;
2818 }
2819 }
2821 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2822 HeapRegionClosure *cl) {
2823 if (r == NULL) {
2824 // The CSet is empty so there's nothing to do.
2825 return;
2826 }
2828 assert(r->in_collection_set(),
2829 "Start region must be a member of the collection set.");
2830 HeapRegion* cur = r;
2831 while (cur != NULL) {
2832 HeapRegion* next = cur->next_in_collection_set();
2833 if (cl->doHeapRegion(cur) && false) {
2834 cl->incomplete();
2835 return;
2836 }
2837 cur = next;
2838 }
2839 cur = g1_policy()->collection_set();
2840 while (cur != r) {
2841 HeapRegion* next = cur->next_in_collection_set();
2842 if (cl->doHeapRegion(cur) && false) {
2843 cl->incomplete();
2844 return;
2845 }
2846 cur = next;
2847 }
2848 }
2850 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2851 HeapRegion* result = _hrm.next_region_in_heap(from);
2852 while (result != NULL && result->isHumongous()) {
2853 result = _hrm.next_region_in_heap(result);
2854 }
2855 return result;
2856 }
2858 Space* G1CollectedHeap::space_containing(const void* addr) const {
2859 return heap_region_containing(addr);
2860 }
2862 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2863 Space* sp = space_containing(addr);
2864 return sp->block_start(addr);
2865 }
2867 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2868 Space* sp = space_containing(addr);
2869 return sp->block_size(addr);
2870 }
2872 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2873 Space* sp = space_containing(addr);
2874 return sp->block_is_obj(addr);
2875 }
2877 bool G1CollectedHeap::supports_tlab_allocation() const {
2878 return true;
2879 }
2881 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2882 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2883 }
2885 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2886 return young_list()->eden_used_bytes();
2887 }
2889 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2890 // must be smaller than the humongous object limit.
2891 size_t G1CollectedHeap::max_tlab_size() const {
2892 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2893 }
2895 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2896 // Return the remaining space in the cur alloc region, but not less than
2897 // the min TLAB size.
2899 // Also, this value can be at most the humongous object threshold,
2900 // since we can't allow tlabs to grow big enough to accommodate
2901 // humongous objects.
2903 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2904 size_t max_tlab = max_tlab_size() * wordSize;
2905 if (hr == NULL) {
2906 return max_tlab;
2907 } else {
2908 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2909 }
2910 }
2912 size_t G1CollectedHeap::max_capacity() const {
2913 return _hrm.reserved().byte_size();
2914 }
2916 jlong G1CollectedHeap::millis_since_last_gc() {
2917 // assert(false, "NYI");
2918 return 0;
2919 }
2921 void G1CollectedHeap::prepare_for_verify() {
2922 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2923 ensure_parsability(false);
2924 }
2925 g1_rem_set()->prepare_for_verify();
2926 }
2928 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2929 VerifyOption vo) {
2930 switch (vo) {
2931 case VerifyOption_G1UsePrevMarking:
2932 return hr->obj_allocated_since_prev_marking(obj);
2933 case VerifyOption_G1UseNextMarking:
2934 return hr->obj_allocated_since_next_marking(obj);
2935 case VerifyOption_G1UseMarkWord:
2936 return false;
2937 default:
2938 ShouldNotReachHere();
2939 }
2940 return false; // keep some compilers happy
2941 }
2943 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2944 switch (vo) {
2945 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2946 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2947 case VerifyOption_G1UseMarkWord: return NULL;
2948 default: ShouldNotReachHere();
2949 }
2950 return NULL; // keep some compilers happy
2951 }
2953 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2954 switch (vo) {
2955 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2956 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2957 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2958 default: ShouldNotReachHere();
2959 }
2960 return false; // keep some compilers happy
2961 }
2963 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2964 switch (vo) {
2965 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2966 case VerifyOption_G1UseNextMarking: return "NTAMS";
2967 case VerifyOption_G1UseMarkWord: return "NONE";
2968 default: ShouldNotReachHere();
2969 }
2970 return NULL; // keep some compilers happy
2971 }
2973 class VerifyRootsClosure: public OopClosure {
2974 private:
2975 G1CollectedHeap* _g1h;
2976 VerifyOption _vo;
2977 bool _failures;
2978 public:
2979 // _vo == UsePrevMarking -> use "prev" marking information,
2980 // _vo == UseNextMarking -> use "next" marking information,
2981 // _vo == UseMarkWord -> use mark word from object header.
2982 VerifyRootsClosure(VerifyOption vo) :
2983 _g1h(G1CollectedHeap::heap()),
2984 _vo(vo),
2985 _failures(false) { }
2987 bool failures() { return _failures; }
2989 template <class T> void do_oop_nv(T* p) {
2990 T heap_oop = oopDesc::load_heap_oop(p);
2991 if (!oopDesc::is_null(heap_oop)) {
2992 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2993 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2994 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2995 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2996 if (_vo == VerifyOption_G1UseMarkWord) {
2997 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2998 }
2999 obj->print_on(gclog_or_tty);
3000 _failures = true;
3001 }
3002 }
3003 }
3005 void do_oop(oop* p) { do_oop_nv(p); }
3006 void do_oop(narrowOop* p) { do_oop_nv(p); }
3007 };
3009 class G1VerifyCodeRootOopClosure: public OopClosure {
3010 G1CollectedHeap* _g1h;
3011 OopClosure* _root_cl;
3012 nmethod* _nm;
3013 VerifyOption _vo;
3014 bool _failures;
3016 template <class T> void do_oop_work(T* p) {
3017 // First verify that this root is live
3018 _root_cl->do_oop(p);
3020 if (!G1VerifyHeapRegionCodeRoots) {
3021 // We're not verifying the code roots attached to heap region.
3022 return;
3023 }
3025 // Don't check the code roots during marking verification in a full GC
3026 if (_vo == VerifyOption_G1UseMarkWord) {
3027 return;
3028 }
3030 // Now verify that the current nmethod (which contains p) is
3031 // in the code root list of the heap region containing the
3032 // object referenced by p.
3034 T heap_oop = oopDesc::load_heap_oop(p);
3035 if (!oopDesc::is_null(heap_oop)) {
3036 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3038 // Now fetch the region containing the object
3039 HeapRegion* hr = _g1h->heap_region_containing(obj);
3040 HeapRegionRemSet* hrrs = hr->rem_set();
3041 // Verify that the strong code root list for this region
3042 // contains the nmethod
3043 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3044 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3045 "from nmethod "PTR_FORMAT" not in strong "
3046 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3047 p, _nm, hr->bottom(), hr->end());
3048 _failures = true;
3049 }
3050 }
3051 }
3053 public:
3054 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3055 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3057 void do_oop(oop* p) { do_oop_work(p); }
3058 void do_oop(narrowOop* p) { do_oop_work(p); }
3060 void set_nmethod(nmethod* nm) { _nm = nm; }
3061 bool failures() { return _failures; }
3062 };
3064 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3065 G1VerifyCodeRootOopClosure* _oop_cl;
3067 public:
3068 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3069 _oop_cl(oop_cl) {}
3071 void do_code_blob(CodeBlob* cb) {
3072 nmethod* nm = cb->as_nmethod_or_null();
3073 if (nm != NULL) {
3074 _oop_cl->set_nmethod(nm);
3075 nm->oops_do(_oop_cl);
3076 }
3077 }
3078 };
3080 class YoungRefCounterClosure : public OopClosure {
3081 G1CollectedHeap* _g1h;
3082 int _count;
3083 public:
3084 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3085 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3086 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3088 int count() { return _count; }
3089 void reset_count() { _count = 0; };
3090 };
3092 class VerifyKlassClosure: public KlassClosure {
3093 YoungRefCounterClosure _young_ref_counter_closure;
3094 OopClosure *_oop_closure;
3095 public:
3096 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3097 void do_klass(Klass* k) {
3098 k->oops_do(_oop_closure);
3100 _young_ref_counter_closure.reset_count();
3101 k->oops_do(&_young_ref_counter_closure);
3102 if (_young_ref_counter_closure.count() > 0) {
3103 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3104 }
3105 }
3106 };
3108 class VerifyLivenessOopClosure: public OopClosure {
3109 G1CollectedHeap* _g1h;
3110 VerifyOption _vo;
3111 public:
3112 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3113 _g1h(g1h), _vo(vo)
3114 { }
3115 void do_oop(narrowOop *p) { do_oop_work(p); }
3116 void do_oop( oop *p) { do_oop_work(p); }
3118 template <class T> void do_oop_work(T *p) {
3119 oop obj = oopDesc::load_decode_heap_oop(p);
3120 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3121 "Dead object referenced by a not dead object");
3122 }
3123 };
3125 class VerifyObjsInRegionClosure: public ObjectClosure {
3126 private:
3127 G1CollectedHeap* _g1h;
3128 size_t _live_bytes;
3129 HeapRegion *_hr;
3130 VerifyOption _vo;
3131 public:
3132 // _vo == UsePrevMarking -> use "prev" marking information,
3133 // _vo == UseNextMarking -> use "next" marking information,
3134 // _vo == UseMarkWord -> use mark word from object header.
3135 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3136 : _live_bytes(0), _hr(hr), _vo(vo) {
3137 _g1h = G1CollectedHeap::heap();
3138 }
3139 void do_object(oop o) {
3140 VerifyLivenessOopClosure isLive(_g1h, _vo);
3141 assert(o != NULL, "Huh?");
3142 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3143 // If the object is alive according to the mark word,
3144 // then verify that the marking information agrees.
3145 // Note we can't verify the contra-positive of the
3146 // above: if the object is dead (according to the mark
3147 // word), it may not be marked, or may have been marked
3148 // but has since became dead, or may have been allocated
3149 // since the last marking.
3150 if (_vo == VerifyOption_G1UseMarkWord) {
3151 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3152 }
3154 o->oop_iterate_no_header(&isLive);
3155 if (!_hr->obj_allocated_since_prev_marking(o)) {
3156 size_t obj_size = o->size(); // Make sure we don't overflow
3157 _live_bytes += (obj_size * HeapWordSize);
3158 }
3159 }
3160 }
3161 size_t live_bytes() { return _live_bytes; }
3162 };
3164 class PrintObjsInRegionClosure : public ObjectClosure {
3165 HeapRegion *_hr;
3166 G1CollectedHeap *_g1;
3167 public:
3168 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3169 _g1 = G1CollectedHeap::heap();
3170 };
3172 void do_object(oop o) {
3173 if (o != NULL) {
3174 HeapWord *start = (HeapWord *) o;
3175 size_t word_sz = o->size();
3176 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3177 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3178 (void*) o, word_sz,
3179 _g1->isMarkedPrev(o),
3180 _g1->isMarkedNext(o),
3181 _hr->obj_allocated_since_prev_marking(o));
3182 HeapWord *end = start + word_sz;
3183 HeapWord *cur;
3184 int *val;
3185 for (cur = start; cur < end; cur++) {
3186 val = (int *) cur;
3187 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3188 }
3189 }
3190 }
3191 };
3193 class VerifyRegionClosure: public HeapRegionClosure {
3194 private:
3195 bool _par;
3196 VerifyOption _vo;
3197 bool _failures;
3198 public:
3199 // _vo == UsePrevMarking -> use "prev" marking information,
3200 // _vo == UseNextMarking -> use "next" marking information,
3201 // _vo == UseMarkWord -> use mark word from object header.
3202 VerifyRegionClosure(bool par, VerifyOption vo)
3203 : _par(par),
3204 _vo(vo),
3205 _failures(false) {}
3207 bool failures() {
3208 return _failures;
3209 }
3211 bool doHeapRegion(HeapRegion* r) {
3212 if (!r->continuesHumongous()) {
3213 bool failures = false;
3214 r->verify(_vo, &failures);
3215 if (failures) {
3216 _failures = true;
3217 } else {
3218 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3219 r->object_iterate(¬_dead_yet_cl);
3220 if (_vo != VerifyOption_G1UseNextMarking) {
3221 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3222 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3223 "max_live_bytes "SIZE_FORMAT" "
3224 "< calculated "SIZE_FORMAT,
3225 r->bottom(), r->end(),
3226 r->max_live_bytes(),
3227 not_dead_yet_cl.live_bytes());
3228 _failures = true;
3229 }
3230 } else {
3231 // When vo == UseNextMarking we cannot currently do a sanity
3232 // check on the live bytes as the calculation has not been
3233 // finalized yet.
3234 }
3235 }
3236 }
3237 return false; // stop the region iteration if we hit a failure
3238 }
3239 };
3241 // This is the task used for parallel verification of the heap regions
3243 class G1ParVerifyTask: public AbstractGangTask {
3244 private:
3245 G1CollectedHeap* _g1h;
3246 VerifyOption _vo;
3247 bool _failures;
3249 public:
3250 // _vo == UsePrevMarking -> use "prev" marking information,
3251 // _vo == UseNextMarking -> use "next" marking information,
3252 // _vo == UseMarkWord -> use mark word from object header.
3253 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3254 AbstractGangTask("Parallel verify task"),
3255 _g1h(g1h),
3256 _vo(vo),
3257 _failures(false) { }
3259 bool failures() {
3260 return _failures;
3261 }
3263 void work(uint worker_id) {
3264 HandleMark hm;
3265 VerifyRegionClosure blk(true, _vo);
3266 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3267 _g1h->workers()->active_workers(),
3268 HeapRegion::ParVerifyClaimValue);
3269 if (blk.failures()) {
3270 _failures = true;
3271 }
3272 }
3273 };
3275 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3276 if (SafepointSynchronize::is_at_safepoint()) {
3277 assert(Thread::current()->is_VM_thread(),
3278 "Expected to be executed serially by the VM thread at this point");
3280 if (!silent) { gclog_or_tty->print("Roots "); }
3281 VerifyRootsClosure rootsCl(vo);
3282 VerifyKlassClosure klassCl(this, &rootsCl);
3283 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3285 // We apply the relevant closures to all the oops in the
3286 // system dictionary, class loader data graph, the string table
3287 // and the nmethods in the code cache.
3288 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3289 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3291 {
3292 G1RootProcessor root_processor(this);
3293 root_processor.process_all_roots(&rootsCl,
3294 &cldCl,
3295 &blobsCl);
3296 }
3298 bool failures = rootsCl.failures() || codeRootsCl.failures();
3300 if (vo != VerifyOption_G1UseMarkWord) {
3301 // If we're verifying during a full GC then the region sets
3302 // will have been torn down at the start of the GC. Therefore
3303 // verifying the region sets will fail. So we only verify
3304 // the region sets when not in a full GC.
3305 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3306 verify_region_sets();
3307 }
3309 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3310 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3311 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3312 "sanity check");
3314 G1ParVerifyTask task(this, vo);
3315 assert(UseDynamicNumberOfGCThreads ||
3316 workers()->active_workers() == workers()->total_workers(),
3317 "If not dynamic should be using all the workers");
3318 int n_workers = workers()->active_workers();
3319 set_par_threads(n_workers);
3320 workers()->run_task(&task);
3321 set_par_threads(0);
3322 if (task.failures()) {
3323 failures = true;
3324 }
3326 // Checks that the expected amount of parallel work was done.
3327 // The implication is that n_workers is > 0.
3328 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3329 "sanity check");
3331 reset_heap_region_claim_values();
3333 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3334 "sanity check");
3335 } else {
3336 VerifyRegionClosure blk(false, vo);
3337 heap_region_iterate(&blk);
3338 if (blk.failures()) {
3339 failures = true;
3340 }
3341 }
3342 if (!silent) gclog_or_tty->print("RemSet ");
3343 rem_set()->verify();
3345 if (G1StringDedup::is_enabled()) {
3346 if (!silent) gclog_or_tty->print("StrDedup ");
3347 G1StringDedup::verify();
3348 }
3350 if (failures) {
3351 gclog_or_tty->print_cr("Heap:");
3352 // It helps to have the per-region information in the output to
3353 // help us track down what went wrong. This is why we call
3354 // print_extended_on() instead of print_on().
3355 print_extended_on(gclog_or_tty);
3356 gclog_or_tty->cr();
3357 #ifndef PRODUCT
3358 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3359 concurrent_mark()->print_reachable("at-verification-failure",
3360 vo, false /* all */);
3361 }
3362 #endif
3363 gclog_or_tty->flush();
3364 }
3365 guarantee(!failures, "there should not have been any failures");
3366 } else {
3367 if (!silent) {
3368 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3369 if (G1StringDedup::is_enabled()) {
3370 gclog_or_tty->print(", StrDedup");
3371 }
3372 gclog_or_tty->print(") ");
3373 }
3374 }
3375 }
3377 void G1CollectedHeap::verify(bool silent) {
3378 verify(silent, VerifyOption_G1UsePrevMarking);
3379 }
3381 double G1CollectedHeap::verify(bool guard, const char* msg) {
3382 double verify_time_ms = 0.0;
3384 if (guard && total_collections() >= VerifyGCStartAt) {
3385 double verify_start = os::elapsedTime();
3386 HandleMark hm; // Discard invalid handles created during verification
3387 prepare_for_verify();
3388 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3389 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3390 }
3392 return verify_time_ms;
3393 }
3395 void G1CollectedHeap::verify_before_gc() {
3396 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3397 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3398 }
3400 void G1CollectedHeap::verify_after_gc() {
3401 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3402 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3403 }
3405 class PrintRegionClosure: public HeapRegionClosure {
3406 outputStream* _st;
3407 public:
3408 PrintRegionClosure(outputStream* st) : _st(st) {}
3409 bool doHeapRegion(HeapRegion* r) {
3410 r->print_on(_st);
3411 return false;
3412 }
3413 };
3415 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3416 const HeapRegion* hr,
3417 const VerifyOption vo) const {
3418 switch (vo) {
3419 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3420 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3421 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3422 default: ShouldNotReachHere();
3423 }
3424 return false; // keep some compilers happy
3425 }
3427 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3428 const VerifyOption vo) const {
3429 switch (vo) {
3430 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3431 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3432 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3433 default: ShouldNotReachHere();
3434 }
3435 return false; // keep some compilers happy
3436 }
3438 void G1CollectedHeap::print_on(outputStream* st) const {
3439 st->print(" %-20s", "garbage-first heap");
3440 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3441 capacity()/K, used_unlocked()/K);
3442 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3443 _hrm.reserved().start(),
3444 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3445 _hrm.reserved().end());
3446 st->cr();
3447 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3448 uint young_regions = _young_list->length();
3449 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3450 (size_t) young_regions * HeapRegion::GrainBytes / K);
3451 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3452 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3453 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3454 st->cr();
3455 MetaspaceAux::print_on(st);
3456 }
3458 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3459 print_on(st);
3461 // Print the per-region information.
3462 st->cr();
3463 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3464 "HS=humongous(starts), HC=humongous(continues), "
3465 "CS=collection set, F=free, TS=gc time stamp, "
3466 "PTAMS=previous top-at-mark-start, "
3467 "NTAMS=next top-at-mark-start)");
3468 PrintRegionClosure blk(st);
3469 heap_region_iterate(&blk);
3470 }
3472 void G1CollectedHeap::print_on_error(outputStream* st) const {
3473 this->CollectedHeap::print_on_error(st);
3475 if (_cm != NULL) {
3476 st->cr();
3477 _cm->print_on_error(st);
3478 }
3479 }
3481 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3482 if (G1CollectedHeap::use_parallel_gc_threads()) {
3483 workers()->print_worker_threads_on(st);
3484 }
3485 _cmThread->print_on(st);
3486 st->cr();
3487 _cm->print_worker_threads_on(st);
3488 _cg1r->print_worker_threads_on(st);
3489 if (G1StringDedup::is_enabled()) {
3490 G1StringDedup::print_worker_threads_on(st);
3491 }
3492 }
3494 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3495 if (G1CollectedHeap::use_parallel_gc_threads()) {
3496 workers()->threads_do(tc);
3497 }
3498 tc->do_thread(_cmThread);
3499 _cg1r->threads_do(tc);
3500 if (G1StringDedup::is_enabled()) {
3501 G1StringDedup::threads_do(tc);
3502 }
3503 }
3505 void G1CollectedHeap::print_tracing_info() const {
3506 // We'll overload this to mean "trace GC pause statistics."
3507 if (TraceGen0Time || TraceGen1Time) {
3508 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3509 // to that.
3510 g1_policy()->print_tracing_info();
3511 }
3512 if (G1SummarizeRSetStats) {
3513 g1_rem_set()->print_summary_info();
3514 }
3515 if (G1SummarizeConcMark) {
3516 concurrent_mark()->print_summary_info();
3517 }
3518 g1_policy()->print_yg_surv_rate_info();
3519 SpecializationStats::print();
3520 }
3522 #ifndef PRODUCT
3523 // Helpful for debugging RSet issues.
3525 class PrintRSetsClosure : public HeapRegionClosure {
3526 private:
3527 const char* _msg;
3528 size_t _occupied_sum;
3530 public:
3531 bool doHeapRegion(HeapRegion* r) {
3532 HeapRegionRemSet* hrrs = r->rem_set();
3533 size_t occupied = hrrs->occupied();
3534 _occupied_sum += occupied;
3536 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3537 HR_FORMAT_PARAMS(r));
3538 if (occupied == 0) {
3539 gclog_or_tty->print_cr(" RSet is empty");
3540 } else {
3541 hrrs->print();
3542 }
3543 gclog_or_tty->print_cr("----------");
3544 return false;
3545 }
3547 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3548 gclog_or_tty->cr();
3549 gclog_or_tty->print_cr("========================================");
3550 gclog_or_tty->print_cr("%s", msg);
3551 gclog_or_tty->cr();
3552 }
3554 ~PrintRSetsClosure() {
3555 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3556 gclog_or_tty->print_cr("========================================");
3557 gclog_or_tty->cr();
3558 }
3559 };
3561 void G1CollectedHeap::print_cset_rsets() {
3562 PrintRSetsClosure cl("Printing CSet RSets");
3563 collection_set_iterate(&cl);
3564 }
3566 void G1CollectedHeap::print_all_rsets() {
3567 PrintRSetsClosure cl("Printing All RSets");;
3568 heap_region_iterate(&cl);
3569 }
3570 #endif // PRODUCT
3572 G1CollectedHeap* G1CollectedHeap::heap() {
3573 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3574 "not a garbage-first heap");
3575 return _g1h;
3576 }
3578 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3579 // always_do_update_barrier = false;
3580 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3581 // Fill TLAB's and such
3582 accumulate_statistics_all_tlabs();
3583 ensure_parsability(true);
3585 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3586 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3587 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3588 }
3589 }
3591 void G1CollectedHeap::gc_epilogue(bool full) {
3593 if (G1SummarizeRSetStats &&
3594 (G1SummarizeRSetStatsPeriod > 0) &&
3595 // we are at the end of the GC. Total collections has already been increased.
3596 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3597 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3598 }
3600 // FIXME: what is this about?
3601 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3602 // is set.
3603 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3604 "derived pointer present"));
3605 // always_do_update_barrier = true;
3607 resize_all_tlabs();
3608 allocation_context_stats().update(full);
3610 // We have just completed a GC. Update the soft reference
3611 // policy with the new heap occupancy
3612 Universe::update_heap_info_at_gc();
3613 }
3615 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3616 unsigned int gc_count_before,
3617 bool* succeeded,
3618 GCCause::Cause gc_cause) {
3619 assert_heap_not_locked_and_not_at_safepoint();
3620 g1_policy()->record_stop_world_start();
3621 VM_G1IncCollectionPause op(gc_count_before,
3622 word_size,
3623 false, /* should_initiate_conc_mark */
3624 g1_policy()->max_pause_time_ms(),
3625 gc_cause);
3627 op.set_allocation_context(AllocationContext::current());
3628 VMThread::execute(&op);
3630 HeapWord* result = op.result();
3631 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3632 assert(result == NULL || ret_succeeded,
3633 "the result should be NULL if the VM did not succeed");
3634 *succeeded = ret_succeeded;
3636 assert_heap_not_locked();
3637 return result;
3638 }
3640 void
3641 G1CollectedHeap::doConcurrentMark() {
3642 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3643 if (!_cmThread->in_progress()) {
3644 _cmThread->set_started();
3645 CGC_lock->notify();
3646 }
3647 }
3649 size_t G1CollectedHeap::pending_card_num() {
3650 size_t extra_cards = 0;
3651 JavaThread *curr = Threads::first();
3652 while (curr != NULL) {
3653 DirtyCardQueue& dcq = curr->dirty_card_queue();
3654 extra_cards += dcq.size();
3655 curr = curr->next();
3656 }
3657 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3658 size_t buffer_size = dcqs.buffer_size();
3659 size_t buffer_num = dcqs.completed_buffers_num();
3661 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3662 // in bytes - not the number of 'entries'. We need to convert
3663 // into a number of cards.
3664 return (buffer_size * buffer_num + extra_cards) / oopSize;
3665 }
3667 size_t G1CollectedHeap::cards_scanned() {
3668 return g1_rem_set()->cardsScanned();
3669 }
3671 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3672 HeapRegion* region = region_at(index);
3673 assert(region->startsHumongous(), "Must start a humongous object");
3674 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3675 }
3677 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3678 private:
3679 size_t _total_humongous;
3680 size_t _candidate_humongous;
3681 public:
3682 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3683 }
3685 virtual bool doHeapRegion(HeapRegion* r) {
3686 if (!r->startsHumongous()) {
3687 return false;
3688 }
3689 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3691 uint region_idx = r->hrm_index();
3692 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3693 // Is_candidate already filters out humongous regions with some remembered set.
3694 // This will not lead to humongous object that we mistakenly keep alive because
3695 // during young collection the remembered sets will only be added to.
3696 if (is_candidate) {
3697 g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3698 _candidate_humongous++;
3699 }
3700 _total_humongous++;
3702 return false;
3703 }
3705 size_t total_humongous() const { return _total_humongous; }
3706 size_t candidate_humongous() const { return _candidate_humongous; }
3707 };
3709 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3710 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3711 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3712 return;
3713 }
3715 RegisterHumongousWithInCSetFastTestClosure cl;
3716 heap_region_iterate(&cl);
3717 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3718 cl.candidate_humongous());
3719 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3721 if (_has_humongous_reclaim_candidates || G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
3722 clear_humongous_is_live_table();
3723 }
3724 }
3726 void
3727 G1CollectedHeap::setup_surviving_young_words() {
3728 assert(_surviving_young_words == NULL, "pre-condition");
3729 uint array_length = g1_policy()->young_cset_region_length();
3730 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3731 if (_surviving_young_words == NULL) {
3732 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3733 "Not enough space for young surv words summary.");
3734 }
3735 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3736 #ifdef ASSERT
3737 for (uint i = 0; i < array_length; ++i) {
3738 assert( _surviving_young_words[i] == 0, "memset above" );
3739 }
3740 #endif // !ASSERT
3741 }
3743 void
3744 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3745 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3746 uint array_length = g1_policy()->young_cset_region_length();
3747 for (uint i = 0; i < array_length; ++i) {
3748 _surviving_young_words[i] += surv_young_words[i];
3749 }
3750 }
3752 void
3753 G1CollectedHeap::cleanup_surviving_young_words() {
3754 guarantee( _surviving_young_words != NULL, "pre-condition" );
3755 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3756 _surviving_young_words = NULL;
3757 }
3759 #ifdef ASSERT
3760 class VerifyCSetClosure: public HeapRegionClosure {
3761 public:
3762 bool doHeapRegion(HeapRegion* hr) {
3763 // Here we check that the CSet region's RSet is ready for parallel
3764 // iteration. The fields that we'll verify are only manipulated
3765 // when the region is part of a CSet and is collected. Afterwards,
3766 // we reset these fields when we clear the region's RSet (when the
3767 // region is freed) so they are ready when the region is
3768 // re-allocated. The only exception to this is if there's an
3769 // evacuation failure and instead of freeing the region we leave
3770 // it in the heap. In that case, we reset these fields during
3771 // evacuation failure handling.
3772 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3774 // Here's a good place to add any other checks we'd like to
3775 // perform on CSet regions.
3776 return false;
3777 }
3778 };
3779 #endif // ASSERT
3781 #if TASKQUEUE_STATS
3782 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3783 st->print_raw_cr("GC Task Stats");
3784 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3785 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3786 }
3788 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3789 print_taskqueue_stats_hdr(st);
3791 TaskQueueStats totals;
3792 const int n = workers() != NULL ? workers()->total_workers() : 1;
3793 for (int i = 0; i < n; ++i) {
3794 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3795 totals += task_queue(i)->stats;
3796 }
3797 st->print_raw("tot "); totals.print(st); st->cr();
3799 DEBUG_ONLY(totals.verify());
3800 }
3802 void G1CollectedHeap::reset_taskqueue_stats() {
3803 const int n = workers() != NULL ? workers()->total_workers() : 1;
3804 for (int i = 0; i < n; ++i) {
3805 task_queue(i)->stats.reset();
3806 }
3807 }
3808 #endif // TASKQUEUE_STATS
3810 void G1CollectedHeap::log_gc_header() {
3811 if (!G1Log::fine()) {
3812 return;
3813 }
3815 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3817 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3818 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3819 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3821 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3822 }
3824 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3825 if (!G1Log::fine()) {
3826 return;
3827 }
3829 if (G1Log::finer()) {
3830 if (evacuation_failed()) {
3831 gclog_or_tty->print(" (to-space exhausted)");
3832 }
3833 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3834 g1_policy()->phase_times()->note_gc_end();
3835 g1_policy()->phase_times()->print(pause_time_sec);
3836 g1_policy()->print_detailed_heap_transition();
3837 } else {
3838 if (evacuation_failed()) {
3839 gclog_or_tty->print("--");
3840 }
3841 g1_policy()->print_heap_transition();
3842 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3843 }
3844 gclog_or_tty->flush();
3845 }
3847 bool
3848 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3849 assert_at_safepoint(true /* should_be_vm_thread */);
3850 guarantee(!is_gc_active(), "collection is not reentrant");
3852 if (GC_locker::check_active_before_gc()) {
3853 return false;
3854 }
3856 _gc_timer_stw->register_gc_start();
3858 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3860 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3861 ResourceMark rm;
3863 print_heap_before_gc();
3864 trace_heap_before_gc(_gc_tracer_stw);
3866 verify_region_sets_optional();
3867 verify_dirty_young_regions();
3869 // This call will decide whether this pause is an initial-mark
3870 // pause. If it is, during_initial_mark_pause() will return true
3871 // for the duration of this pause.
3872 g1_policy()->decide_on_conc_mark_initiation();
3874 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3875 assert(!g1_policy()->during_initial_mark_pause() ||
3876 g1_policy()->gcs_are_young(), "sanity");
3878 // We also do not allow mixed GCs during marking.
3879 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3881 // Record whether this pause is an initial mark. When the current
3882 // thread has completed its logging output and it's safe to signal
3883 // the CM thread, the flag's value in the policy has been reset.
3884 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3886 // Inner scope for scope based logging, timers, and stats collection
3887 {
3888 EvacuationInfo evacuation_info;
3890 if (g1_policy()->during_initial_mark_pause()) {
3891 // We are about to start a marking cycle, so we increment the
3892 // full collection counter.
3893 increment_old_marking_cycles_started();
3894 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3895 }
3897 _gc_tracer_stw->report_yc_type(yc_type());
3899 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3901 uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3902 workers()->active_workers() : 1);
3903 double pause_start_sec = os::elapsedTime();
3904 g1_policy()->phase_times()->note_gc_start(active_workers, mark_in_progress());
3905 log_gc_header();
3907 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3908 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3910 // If the secondary_free_list is not empty, append it to the
3911 // free_list. No need to wait for the cleanup operation to finish;
3912 // the region allocation code will check the secondary_free_list
3913 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3914 // set, skip this step so that the region allocation code has to
3915 // get entries from the secondary_free_list.
3916 if (!G1StressConcRegionFreeing) {
3917 append_secondary_free_list_if_not_empty_with_lock();
3918 }
3920 assert(check_young_list_well_formed(), "young list should be well formed");
3921 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3922 "sanity check");
3924 // Don't dynamically change the number of GC threads this early. A value of
3925 // 0 is used to indicate serial work. When parallel work is done,
3926 // it will be set.
3928 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3929 IsGCActiveMark x;
3931 gc_prologue(false);
3932 increment_total_collections(false /* full gc */);
3933 increment_gc_time_stamp();
3935 verify_before_gc();
3936 check_bitmaps("GC Start");
3938 COMPILER2_PRESENT(DerivedPointerTable::clear());
3940 // Please see comment in g1CollectedHeap.hpp and
3941 // G1CollectedHeap::ref_processing_init() to see how
3942 // reference processing currently works in G1.
3944 // Enable discovery in the STW reference processor
3945 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3946 true /*verify_no_refs*/);
3948 {
3949 // We want to temporarily turn off discovery by the
3950 // CM ref processor, if necessary, and turn it back on
3951 // on again later if we do. Using a scoped
3952 // NoRefDiscovery object will do this.
3953 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3955 // Forget the current alloc region (we might even choose it to be part
3956 // of the collection set!).
3957 _allocator->release_mutator_alloc_region();
3959 // We should call this after we retire the mutator alloc
3960 // region(s) so that all the ALLOC / RETIRE events are generated
3961 // before the start GC event.
3962 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3964 // This timing is only used by the ergonomics to handle our pause target.
3965 // It is unclear why this should not include the full pause. We will
3966 // investigate this in CR 7178365.
3967 //
3968 // Preserving the old comment here if that helps the investigation:
3969 //
3970 // The elapsed time induced by the start time below deliberately elides
3971 // the possible verification above.
3972 double sample_start_time_sec = os::elapsedTime();
3974 #if YOUNG_LIST_VERBOSE
3975 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3976 _young_list->print();
3977 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3978 #endif // YOUNG_LIST_VERBOSE
3980 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3982 double scan_wait_start = os::elapsedTime();
3983 // We have to wait until the CM threads finish scanning the
3984 // root regions as it's the only way to ensure that all the
3985 // objects on them have been correctly scanned before we start
3986 // moving them during the GC.
3987 bool waited = _cm->root_regions()->wait_until_scan_finished();
3988 double wait_time_ms = 0.0;
3989 if (waited) {
3990 double scan_wait_end = os::elapsedTime();
3991 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3992 }
3993 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3995 #if YOUNG_LIST_VERBOSE
3996 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3997 _young_list->print();
3998 #endif // YOUNG_LIST_VERBOSE
4000 if (g1_policy()->during_initial_mark_pause()) {
4001 concurrent_mark()->checkpointRootsInitialPre();
4002 }
4004 #if YOUNG_LIST_VERBOSE
4005 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4006 _young_list->print();
4007 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4008 #endif // YOUNG_LIST_VERBOSE
4010 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4012 register_humongous_regions_with_in_cset_fast_test();
4014 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
4016 _cm->note_start_of_gc();
4017 // We should not verify the per-thread SATB buffers given that
4018 // we have not filtered them yet (we'll do so during the
4019 // GC). We also call this after finalize_cset() to
4020 // ensure that the CSet has been finalized.
4021 _cm->verify_no_cset_oops(true /* verify_stacks */,
4022 true /* verify_enqueued_buffers */,
4023 false /* verify_thread_buffers */,
4024 true /* verify_fingers */);
4026 if (_hr_printer.is_active()) {
4027 HeapRegion* hr = g1_policy()->collection_set();
4028 while (hr != NULL) {
4029 _hr_printer.cset(hr);
4030 hr = hr->next_in_collection_set();
4031 }
4032 }
4034 #ifdef ASSERT
4035 VerifyCSetClosure cl;
4036 collection_set_iterate(&cl);
4037 #endif // ASSERT
4039 setup_surviving_young_words();
4041 // Initialize the GC alloc regions.
4042 _allocator->init_gc_alloc_regions(evacuation_info);
4044 // Actually do the work...
4045 evacuate_collection_set(evacuation_info);
4047 // We do this to mainly verify the per-thread SATB buffers
4048 // (which have been filtered by now) since we didn't verify
4049 // them earlier. No point in re-checking the stacks / enqueued
4050 // buffers given that the CSet has not changed since last time
4051 // we checked.
4052 _cm->verify_no_cset_oops(false /* verify_stacks */,
4053 false /* verify_enqueued_buffers */,
4054 true /* verify_thread_buffers */,
4055 true /* verify_fingers */);
4057 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4059 eagerly_reclaim_humongous_regions();
4061 g1_policy()->clear_collection_set();
4063 cleanup_surviving_young_words();
4065 // Start a new incremental collection set for the next pause.
4066 g1_policy()->start_incremental_cset_building();
4068 clear_cset_fast_test();
4070 _young_list->reset_sampled_info();
4072 // Don't check the whole heap at this point as the
4073 // GC alloc regions from this pause have been tagged
4074 // as survivors and moved on to the survivor list.
4075 // Survivor regions will fail the !is_young() check.
4076 assert(check_young_list_empty(false /* check_heap */),
4077 "young list should be empty");
4079 #if YOUNG_LIST_VERBOSE
4080 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4081 _young_list->print();
4082 #endif // YOUNG_LIST_VERBOSE
4084 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4085 _young_list->first_survivor_region(),
4086 _young_list->last_survivor_region());
4088 _young_list->reset_auxilary_lists();
4090 if (evacuation_failed()) {
4091 _allocator->set_used(recalculate_used());
4092 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4093 for (uint i = 0; i < n_queues; i++) {
4094 if (_evacuation_failed_info_array[i].has_failed()) {
4095 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4096 }
4097 }
4098 } else {
4099 // The "used" of the the collection set have already been subtracted
4100 // when they were freed. Add in the bytes evacuated.
4101 _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
4102 }
4104 if (g1_policy()->during_initial_mark_pause()) {
4105 // We have to do this before we notify the CM threads that
4106 // they can start working to make sure that all the
4107 // appropriate initialization is done on the CM object.
4108 concurrent_mark()->checkpointRootsInitialPost();
4109 set_marking_started();
4110 // Note that we don't actually trigger the CM thread at
4111 // this point. We do that later when we're sure that
4112 // the current thread has completed its logging output.
4113 }
4115 allocate_dummy_regions();
4117 #if YOUNG_LIST_VERBOSE
4118 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4119 _young_list->print();
4120 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4121 #endif // YOUNG_LIST_VERBOSE
4123 _allocator->init_mutator_alloc_region();
4125 {
4126 size_t expand_bytes = g1_policy()->expansion_amount();
4127 if (expand_bytes > 0) {
4128 size_t bytes_before = capacity();
4129 // No need for an ergo verbose message here,
4130 // expansion_amount() does this when it returns a value > 0.
4131 if (!expand(expand_bytes)) {
4132 // We failed to expand the heap. Cannot do anything about it.
4133 }
4134 }
4135 }
4137 // We redo the verification but now wrt to the new CSet which
4138 // has just got initialized after the previous CSet was freed.
4139 _cm->verify_no_cset_oops(true /* verify_stacks */,
4140 true /* verify_enqueued_buffers */,
4141 true /* verify_thread_buffers */,
4142 true /* verify_fingers */);
4143 _cm->note_end_of_gc();
4145 // This timing is only used by the ergonomics to handle our pause target.
4146 // It is unclear why this should not include the full pause. We will
4147 // investigate this in CR 7178365.
4148 double sample_end_time_sec = os::elapsedTime();
4149 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4150 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4152 MemoryService::track_memory_usage();
4154 // In prepare_for_verify() below we'll need to scan the deferred
4155 // update buffers to bring the RSets up-to-date if
4156 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4157 // the update buffers we'll probably need to scan cards on the
4158 // regions we just allocated to (i.e., the GC alloc
4159 // regions). However, during the last GC we called
4160 // set_saved_mark() on all the GC alloc regions, so card
4161 // scanning might skip the [saved_mark_word()...top()] area of
4162 // those regions (i.e., the area we allocated objects into
4163 // during the last GC). But it shouldn't. Given that
4164 // saved_mark_word() is conditional on whether the GC time stamp
4165 // on the region is current or not, by incrementing the GC time
4166 // stamp here we invalidate all the GC time stamps on all the
4167 // regions and saved_mark_word() will simply return top() for
4168 // all the regions. This is a nicer way of ensuring this rather
4169 // than iterating over the regions and fixing them. In fact, the
4170 // GC time stamp increment here also ensures that
4171 // saved_mark_word() will return top() between pauses, i.e.,
4172 // during concurrent refinement. So we don't need the
4173 // is_gc_active() check to decided which top to use when
4174 // scanning cards (see CR 7039627).
4175 increment_gc_time_stamp();
4177 verify_after_gc();
4178 check_bitmaps("GC End");
4180 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4181 ref_processor_stw()->verify_no_references_recorded();
4183 // CM reference discovery will be re-enabled if necessary.
4184 }
4186 // We should do this after we potentially expand the heap so
4187 // that all the COMMIT events are generated before the end GC
4188 // event, and after we retire the GC alloc regions so that all
4189 // RETIRE events are generated before the end GC event.
4190 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4192 #ifdef TRACESPINNING
4193 ParallelTaskTerminator::print_termination_counts();
4194 #endif
4196 gc_epilogue(false);
4197 }
4199 // Print the remainder of the GC log output.
4200 log_gc_footer(os::elapsedTime() - pause_start_sec);
4202 // It is not yet to safe to tell the concurrent mark to
4203 // start as we have some optional output below. We don't want the
4204 // output from the concurrent mark thread interfering with this
4205 // logging output either.
4207 _hrm.verify_optional();
4208 verify_region_sets_optional();
4210 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4211 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4213 print_heap_after_gc();
4214 trace_heap_after_gc(_gc_tracer_stw);
4216 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4217 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4218 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4219 // before any GC notifications are raised.
4220 g1mm()->update_sizes();
4222 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4223 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4224 _gc_timer_stw->register_gc_end();
4225 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4226 }
4227 // It should now be safe to tell the concurrent mark thread to start
4228 // without its logging output interfering with the logging output
4229 // that came from the pause.
4231 if (should_start_conc_mark) {
4232 // CAUTION: after the doConcurrentMark() call below,
4233 // the concurrent marking thread(s) could be running
4234 // concurrently with us. Make sure that anything after
4235 // this point does not assume that we are the only GC thread
4236 // running. Note: of course, the actual marking work will
4237 // not start until the safepoint itself is released in
4238 // SuspendibleThreadSet::desynchronize().
4239 doConcurrentMark();
4240 }
4242 return true;
4243 }
4245 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4246 _drain_in_progress = false;
4247 set_evac_failure_closure(cl);
4248 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4249 }
4251 void G1CollectedHeap::finalize_for_evac_failure() {
4252 assert(_evac_failure_scan_stack != NULL &&
4253 _evac_failure_scan_stack->length() == 0,
4254 "Postcondition");
4255 assert(!_drain_in_progress, "Postcondition");
4256 delete _evac_failure_scan_stack;
4257 _evac_failure_scan_stack = NULL;
4258 }
4260 void G1CollectedHeap::remove_self_forwarding_pointers() {
4261 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4263 double remove_self_forwards_start = os::elapsedTime();
4265 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4267 if (G1CollectedHeap::use_parallel_gc_threads()) {
4268 set_par_threads();
4269 workers()->run_task(&rsfp_task);
4270 set_par_threads(0);
4271 } else {
4272 rsfp_task.work(0);
4273 }
4275 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4277 // Reset the claim values in the regions in the collection set.
4278 reset_cset_heap_region_claim_values();
4280 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4282 // Now restore saved marks, if any.
4283 assert(_objs_with_preserved_marks.size() ==
4284 _preserved_marks_of_objs.size(), "Both or none.");
4285 while (!_objs_with_preserved_marks.is_empty()) {
4286 oop obj = _objs_with_preserved_marks.pop();
4287 markOop m = _preserved_marks_of_objs.pop();
4288 obj->set_mark(m);
4289 }
4290 _objs_with_preserved_marks.clear(true);
4291 _preserved_marks_of_objs.clear(true);
4293 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4294 }
4296 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4297 _evac_failure_scan_stack->push(obj);
4298 }
4300 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4301 assert(_evac_failure_scan_stack != NULL, "precondition");
4303 while (_evac_failure_scan_stack->length() > 0) {
4304 oop obj = _evac_failure_scan_stack->pop();
4305 _evac_failure_closure->set_region(heap_region_containing(obj));
4306 obj->oop_iterate_backwards(_evac_failure_closure);
4307 }
4308 }
4310 oop
4311 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4312 oop old) {
4313 assert(obj_in_cs(old),
4314 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4315 (HeapWord*) old));
4316 markOop m = old->mark();
4317 oop forward_ptr = old->forward_to_atomic(old);
4318 if (forward_ptr == NULL) {
4319 // Forward-to-self succeeded.
4320 assert(_par_scan_state != NULL, "par scan state");
4321 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4322 uint queue_num = _par_scan_state->queue_num();
4324 _evacuation_failed = true;
4325 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4326 if (_evac_failure_closure != cl) {
4327 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4328 assert(!_drain_in_progress,
4329 "Should only be true while someone holds the lock.");
4330 // Set the global evac-failure closure to the current thread's.
4331 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4332 set_evac_failure_closure(cl);
4333 // Now do the common part.
4334 handle_evacuation_failure_common(old, m);
4335 // Reset to NULL.
4336 set_evac_failure_closure(NULL);
4337 } else {
4338 // The lock is already held, and this is recursive.
4339 assert(_drain_in_progress, "This should only be the recursive case.");
4340 handle_evacuation_failure_common(old, m);
4341 }
4342 return old;
4343 } else {
4344 // Forward-to-self failed. Either someone else managed to allocate
4345 // space for this object (old != forward_ptr) or they beat us in
4346 // self-forwarding it (old == forward_ptr).
4347 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4348 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4349 "should not be in the CSet",
4350 (HeapWord*) old, (HeapWord*) forward_ptr));
4351 return forward_ptr;
4352 }
4353 }
4355 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4356 preserve_mark_if_necessary(old, m);
4358 HeapRegion* r = heap_region_containing(old);
4359 if (!r->evacuation_failed()) {
4360 r->set_evacuation_failed(true);
4361 _hr_printer.evac_failure(r);
4362 }
4364 push_on_evac_failure_scan_stack(old);
4366 if (!_drain_in_progress) {
4367 // prevent recursion in copy_to_survivor_space()
4368 _drain_in_progress = true;
4369 drain_evac_failure_scan_stack();
4370 _drain_in_progress = false;
4371 }
4372 }
4374 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4375 assert(evacuation_failed(), "Oversaving!");
4376 // We want to call the "for_promotion_failure" version only in the
4377 // case of a promotion failure.
4378 if (m->must_be_preserved_for_promotion_failure(obj)) {
4379 _objs_with_preserved_marks.push(obj);
4380 _preserved_marks_of_objs.push(m);
4381 }
4382 }
4384 void G1ParCopyHelper::mark_object(oop obj) {
4385 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4387 // We know that the object is not moving so it's safe to read its size.
4388 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4389 }
4391 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4392 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4393 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4394 assert(from_obj != to_obj, "should not be self-forwarded");
4396 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4397 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4399 // The object might be in the process of being copied by another
4400 // worker so we cannot trust that its to-space image is
4401 // well-formed. So we have to read its size from its from-space
4402 // image which we know should not be changing.
4403 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4404 }
4406 template <class T>
4407 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4408 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4409 _scanned_klass->record_modified_oops();
4410 }
4411 }
4413 template <G1Barrier barrier, G1Mark do_mark_object>
4414 template <class T>
4415 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4416 T heap_oop = oopDesc::load_heap_oop(p);
4418 if (oopDesc::is_null(heap_oop)) {
4419 return;
4420 }
4422 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4424 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4426 const InCSetState state = _g1->in_cset_state(obj);
4427 if (state.is_in_cset()) {
4428 oop forwardee;
4429 markOop m = obj->mark();
4430 if (m->is_marked()) {
4431 forwardee = (oop) m->decode_pointer();
4432 } else {
4433 forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4434 }
4435 assert(forwardee != NULL, "forwardee should not be NULL");
4436 oopDesc::encode_store_heap_oop(p, forwardee);
4437 if (do_mark_object != G1MarkNone && forwardee != obj) {
4438 // If the object is self-forwarded we don't need to explicitly
4439 // mark it, the evacuation failure protocol will do so.
4440 mark_forwarded_object(obj, forwardee);
4441 }
4443 if (barrier == G1BarrierKlass) {
4444 do_klass_barrier(p, forwardee);
4445 }
4446 } else {
4447 if (state.is_humongous()) {
4448 _g1->set_humongous_is_live(obj);
4449 }
4450 // The object is not in collection set. If we're a root scanning
4451 // closure during an initial mark pause then attempt to mark the object.
4452 if (do_mark_object == G1MarkFromRoot) {
4453 mark_object(obj);
4454 }
4455 }
4457 if (barrier == G1BarrierEvac) {
4458 _par_scan_state->update_rs(_from, p, _worker_id);
4459 }
4460 }
4462 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4463 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4465 class G1ParEvacuateFollowersClosure : public VoidClosure {
4466 protected:
4467 G1CollectedHeap* _g1h;
4468 G1ParScanThreadState* _par_scan_state;
4469 RefToScanQueueSet* _queues;
4470 ParallelTaskTerminator* _terminator;
4472 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4473 RefToScanQueueSet* queues() { return _queues; }
4474 ParallelTaskTerminator* terminator() { return _terminator; }
4476 public:
4477 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4478 G1ParScanThreadState* par_scan_state,
4479 RefToScanQueueSet* queues,
4480 ParallelTaskTerminator* terminator)
4481 : _g1h(g1h), _par_scan_state(par_scan_state),
4482 _queues(queues), _terminator(terminator) {}
4484 void do_void();
4486 private:
4487 inline bool offer_termination();
4488 };
4490 bool G1ParEvacuateFollowersClosure::offer_termination() {
4491 G1ParScanThreadState* const pss = par_scan_state();
4492 pss->start_term_time();
4493 const bool res = terminator()->offer_termination();
4494 pss->end_term_time();
4495 return res;
4496 }
4498 void G1ParEvacuateFollowersClosure::do_void() {
4499 G1ParScanThreadState* const pss = par_scan_state();
4500 pss->trim_queue();
4501 do {
4502 pss->steal_and_trim_queue(queues());
4503 } while (!offer_termination());
4504 }
4506 class G1KlassScanClosure : public KlassClosure {
4507 G1ParCopyHelper* _closure;
4508 bool _process_only_dirty;
4509 int _count;
4510 public:
4511 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4512 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4513 void do_klass(Klass* klass) {
4514 // If the klass has not been dirtied we know that there's
4515 // no references into the young gen and we can skip it.
4516 if (!_process_only_dirty || klass->has_modified_oops()) {
4517 // Clean the klass since we're going to scavenge all the metadata.
4518 klass->clear_modified_oops();
4520 // Tell the closure that this klass is the Klass to scavenge
4521 // and is the one to dirty if oops are left pointing into the young gen.
4522 _closure->set_scanned_klass(klass);
4524 klass->oops_do(_closure);
4526 _closure->set_scanned_klass(NULL);
4527 }
4528 _count++;
4529 }
4530 };
4532 class G1ParTask : public AbstractGangTask {
4533 protected:
4534 G1CollectedHeap* _g1h;
4535 RefToScanQueueSet *_queues;
4536 G1RootProcessor* _root_processor;
4537 ParallelTaskTerminator _terminator;
4538 uint _n_workers;
4540 Mutex _stats_lock;
4541 Mutex* stats_lock() { return &_stats_lock; }
4543 public:
4544 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor)
4545 : AbstractGangTask("G1 collection"),
4546 _g1h(g1h),
4547 _queues(task_queues),
4548 _root_processor(root_processor),
4549 _terminator(0, _queues),
4550 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4551 {}
4553 RefToScanQueueSet* queues() { return _queues; }
4555 RefToScanQueue *work_queue(int i) {
4556 return queues()->queue(i);
4557 }
4559 ParallelTaskTerminator* terminator() { return &_terminator; }
4561 virtual void set_for_termination(int active_workers) {
4562 _root_processor->set_num_workers(active_workers);
4563 terminator()->reset_for_reuse(active_workers);
4564 _n_workers = active_workers;
4565 }
4567 // Helps out with CLD processing.
4568 //
4569 // During InitialMark we need to:
4570 // 1) Scavenge all CLDs for the young GC.
4571 // 2) Mark all objects directly reachable from strong CLDs.
4572 template <G1Mark do_mark_object>
4573 class G1CLDClosure : public CLDClosure {
4574 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4575 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4576 G1KlassScanClosure _klass_in_cld_closure;
4577 bool _claim;
4579 public:
4580 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4581 bool only_young, bool claim)
4582 : _oop_closure(oop_closure),
4583 _oop_in_klass_closure(oop_closure->g1(),
4584 oop_closure->pss(),
4585 oop_closure->rp()),
4586 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4587 _claim(claim) {
4589 }
4591 void do_cld(ClassLoaderData* cld) {
4592 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4593 }
4594 };
4596 void work(uint worker_id) {
4597 if (worker_id >= _n_workers) return; // no work needed this round
4599 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime());
4601 {
4602 ResourceMark rm;
4603 HandleMark hm;
4605 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4607 G1ParScanThreadState pss(_g1h, worker_id, rp);
4608 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4610 pss.set_evac_failure_closure(&evac_failure_cl);
4612 bool only_young = _g1h->g1_policy()->gcs_are_young();
4614 // Non-IM young GC.
4615 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4616 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4617 only_young, // Only process dirty klasses.
4618 false); // No need to claim CLDs.
4619 // IM young GC.
4620 // Strong roots closures.
4621 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4622 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4623 false, // Process all klasses.
4624 true); // Need to claim CLDs.
4625 // Weak roots closures.
4626 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4627 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4628 false, // Process all klasses.
4629 true); // Need to claim CLDs.
4631 OopClosure* strong_root_cl;
4632 OopClosure* weak_root_cl;
4633 CLDClosure* strong_cld_cl;
4634 CLDClosure* weak_cld_cl;
4636 bool trace_metadata = false;
4638 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4639 // We also need to mark copied objects.
4640 strong_root_cl = &scan_mark_root_cl;
4641 strong_cld_cl = &scan_mark_cld_cl;
4642 if (ClassUnloadingWithConcurrentMark) {
4643 weak_root_cl = &scan_mark_weak_root_cl;
4644 weak_cld_cl = &scan_mark_weak_cld_cl;
4645 trace_metadata = true;
4646 } else {
4647 weak_root_cl = &scan_mark_root_cl;
4648 weak_cld_cl = &scan_mark_cld_cl;
4649 }
4650 } else {
4651 strong_root_cl = &scan_only_root_cl;
4652 weak_root_cl = &scan_only_root_cl;
4653 strong_cld_cl = &scan_only_cld_cl;
4654 weak_cld_cl = &scan_only_cld_cl;
4655 }
4657 pss.start_strong_roots();
4659 _root_processor->evacuate_roots(strong_root_cl,
4660 weak_root_cl,
4661 strong_cld_cl,
4662 weak_cld_cl,
4663 trace_metadata,
4664 worker_id);
4666 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4667 _root_processor->scan_remembered_sets(&push_heap_rs_cl,
4668 weak_root_cl,
4669 worker_id);
4670 pss.end_strong_roots();
4672 {
4673 double start = os::elapsedTime();
4674 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4675 evac.do_void();
4676 double elapsed_sec = os::elapsedTime() - start;
4677 double term_sec = pss.term_time();
4678 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
4679 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
4680 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts());
4681 }
4682 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4683 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4685 if (ParallelGCVerbose) {
4686 MutexLocker x(stats_lock());
4687 pss.print_termination_stats(worker_id);
4688 }
4690 assert(pss.queue_is_empty(), "should be empty");
4692 // Close the inner scope so that the ResourceMark and HandleMark
4693 // destructors are executed here and are included as part of the
4694 // "GC Worker Time".
4695 }
4696 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
4697 }
4698 };
4700 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4701 private:
4702 BoolObjectClosure* _is_alive;
4703 int _initial_string_table_size;
4704 int _initial_symbol_table_size;
4706 bool _process_strings;
4707 int _strings_processed;
4708 int _strings_removed;
4710 bool _process_symbols;
4711 int _symbols_processed;
4712 int _symbols_removed;
4714 bool _do_in_parallel;
4715 public:
4716 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4717 AbstractGangTask("String/Symbol Unlinking"),
4718 _is_alive(is_alive),
4719 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4720 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4721 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4723 _initial_string_table_size = StringTable::the_table()->table_size();
4724 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4725 if (process_strings) {
4726 StringTable::clear_parallel_claimed_index();
4727 }
4728 if (process_symbols) {
4729 SymbolTable::clear_parallel_claimed_index();
4730 }
4731 }
4733 ~G1StringSymbolTableUnlinkTask() {
4734 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4735 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT,
4736 StringTable::parallel_claimed_index(), _initial_string_table_size));
4737 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4738 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT,
4739 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4741 if (G1TraceStringSymbolTableScrubbing) {
4742 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4743 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4744 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4745 strings_processed(), strings_removed(),
4746 symbols_processed(), symbols_removed());
4747 }
4748 }
4750 void work(uint worker_id) {
4751 if (_do_in_parallel) {
4752 int strings_processed = 0;
4753 int strings_removed = 0;
4754 int symbols_processed = 0;
4755 int symbols_removed = 0;
4756 if (_process_strings) {
4757 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4758 Atomic::add(strings_processed, &_strings_processed);
4759 Atomic::add(strings_removed, &_strings_removed);
4760 }
4761 if (_process_symbols) {
4762 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4763 Atomic::add(symbols_processed, &_symbols_processed);
4764 Atomic::add(symbols_removed, &_symbols_removed);
4765 }
4766 } else {
4767 if (_process_strings) {
4768 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4769 }
4770 if (_process_symbols) {
4771 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4772 }
4773 }
4774 }
4776 size_t strings_processed() const { return (size_t)_strings_processed; }
4777 size_t strings_removed() const { return (size_t)_strings_removed; }
4779 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4780 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4781 };
4783 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4784 private:
4785 static Monitor* _lock;
4787 BoolObjectClosure* const _is_alive;
4788 const bool _unloading_occurred;
4789 const uint _num_workers;
4791 // Variables used to claim nmethods.
4792 nmethod* _first_nmethod;
4793 volatile nmethod* _claimed_nmethod;
4795 // The list of nmethods that need to be processed by the second pass.
4796 volatile nmethod* _postponed_list;
4797 volatile uint _num_entered_barrier;
4799 public:
4800 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4801 _is_alive(is_alive),
4802 _unloading_occurred(unloading_occurred),
4803 _num_workers(num_workers),
4804 _first_nmethod(NULL),
4805 _claimed_nmethod(NULL),
4806 _postponed_list(NULL),
4807 _num_entered_barrier(0)
4808 {
4809 nmethod::increase_unloading_clock();
4810 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
4811 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4812 }
4814 ~G1CodeCacheUnloadingTask() {
4815 CodeCache::verify_clean_inline_caches();
4817 CodeCache::set_needs_cache_clean(false);
4818 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4820 CodeCache::verify_icholder_relocations();
4821 }
4823 private:
4824 void add_to_postponed_list(nmethod* nm) {
4825 nmethod* old;
4826 do {
4827 old = (nmethod*)_postponed_list;
4828 nm->set_unloading_next(old);
4829 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4830 }
4832 void clean_nmethod(nmethod* nm) {
4833 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4835 if (postponed) {
4836 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4837 add_to_postponed_list(nm);
4838 }
4840 // Mark that this thread has been cleaned/unloaded.
4841 // After this call, it will be safe to ask if this nmethod was unloaded or not.
4842 nm->set_unloading_clock(nmethod::global_unloading_clock());
4843 }
4845 void clean_nmethod_postponed(nmethod* nm) {
4846 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4847 }
4849 static const int MaxClaimNmethods = 16;
4851 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4852 nmethod* first;
4853 nmethod* last;
4855 do {
4856 *num_claimed_nmethods = 0;
4858 first = last = (nmethod*)_claimed_nmethod;
4860 if (first != NULL) {
4861 for (int i = 0; i < MaxClaimNmethods; i++) {
4862 last = CodeCache::alive_nmethod(CodeCache::next(last));
4864 if (last == NULL) {
4865 break;
4866 }
4868 claimed_nmethods[i] = last;
4869 (*num_claimed_nmethods)++;
4870 }
4871 }
4873 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
4874 }
4876 nmethod* claim_postponed_nmethod() {
4877 nmethod* claim;
4878 nmethod* next;
4880 do {
4881 claim = (nmethod*)_postponed_list;
4882 if (claim == NULL) {
4883 return NULL;
4884 }
4886 next = claim->unloading_next();
4888 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4890 return claim;
4891 }
4893 public:
4894 // Mark that we're done with the first pass of nmethod cleaning.
4895 void barrier_mark(uint worker_id) {
4896 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4897 _num_entered_barrier++;
4898 if (_num_entered_barrier == _num_workers) {
4899 ml.notify_all();
4900 }
4901 }
4903 // See if we have to wait for the other workers to
4904 // finish their first-pass nmethod cleaning work.
4905 void barrier_wait(uint worker_id) {
4906 if (_num_entered_barrier < _num_workers) {
4907 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4908 while (_num_entered_barrier < _num_workers) {
4909 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4910 }
4911 }
4912 }
4914 // Cleaning and unloading of nmethods. Some work has to be postponed
4915 // to the second pass, when we know which nmethods survive.
4916 void work_first_pass(uint worker_id) {
4917 // The first nmethods is claimed by the first worker.
4918 if (worker_id == 0 && _first_nmethod != NULL) {
4919 clean_nmethod(_first_nmethod);
4920 _first_nmethod = NULL;
4921 }
4923 int num_claimed_nmethods;
4924 nmethod* claimed_nmethods[MaxClaimNmethods];
4926 while (true) {
4927 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4929 if (num_claimed_nmethods == 0) {
4930 break;
4931 }
4933 for (int i = 0; i < num_claimed_nmethods; i++) {
4934 clean_nmethod(claimed_nmethods[i]);
4935 }
4936 }
4938 // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark.
4939 // Need to retire the buffers now that this thread has stopped cleaning nmethods.
4940 MetadataOnStackMark::retire_buffer_for_thread(Thread::current());
4941 }
4943 void work_second_pass(uint worker_id) {
4944 nmethod* nm;
4945 // Take care of postponed nmethods.
4946 while ((nm = claim_postponed_nmethod()) != NULL) {
4947 clean_nmethod_postponed(nm);
4948 }
4949 }
4950 };
4952 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
4954 class G1KlassCleaningTask : public StackObj {
4955 BoolObjectClosure* _is_alive;
4956 volatile jint _clean_klass_tree_claimed;
4957 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4959 public:
4960 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4961 _is_alive(is_alive),
4962 _clean_klass_tree_claimed(0),
4963 _klass_iterator() {
4964 }
4966 private:
4967 bool claim_clean_klass_tree_task() {
4968 if (_clean_klass_tree_claimed) {
4969 return false;
4970 }
4972 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4973 }
4975 InstanceKlass* claim_next_klass() {
4976 Klass* klass;
4977 do {
4978 klass =_klass_iterator.next_klass();
4979 } while (klass != NULL && !klass->oop_is_instance());
4981 return (InstanceKlass*)klass;
4982 }
4984 public:
4986 void clean_klass(InstanceKlass* ik) {
4987 ik->clean_implementors_list(_is_alive);
4988 ik->clean_method_data(_is_alive);
4990 // G1 specific cleanup work that has
4991 // been moved here to be done in parallel.
4992 ik->clean_dependent_nmethods();
4993 if (JvmtiExport::has_redefined_a_class()) {
4994 InstanceKlass::purge_previous_versions(ik);
4995 }
4996 }
4998 void work() {
4999 ResourceMark rm;
5001 // One worker will clean the subklass/sibling klass tree.
5002 if (claim_clean_klass_tree_task()) {
5003 Klass::clean_subklass_tree(_is_alive);
5004 }
5006 // All workers will help cleaning the classes,
5007 InstanceKlass* klass;
5008 while ((klass = claim_next_klass()) != NULL) {
5009 clean_klass(klass);
5010 }
5011 }
5012 };
5014 // To minimize the remark pause times, the tasks below are done in parallel.
5015 class G1ParallelCleaningTask : public AbstractGangTask {
5016 private:
5017 G1StringSymbolTableUnlinkTask _string_symbol_task;
5018 G1CodeCacheUnloadingTask _code_cache_task;
5019 G1KlassCleaningTask _klass_cleaning_task;
5021 public:
5022 // The constructor is run in the VMThread.
5023 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5024 AbstractGangTask("Parallel Cleaning"),
5025 _string_symbol_task(is_alive, process_strings, process_symbols),
5026 _code_cache_task(num_workers, is_alive, unloading_occurred),
5027 _klass_cleaning_task(is_alive) {
5028 }
5030 void pre_work_verification() {
5031 // The VM Thread will have registered Metadata during the single-threaded phase of MetadataStackOnMark.
5032 assert(Thread::current()->is_VM_thread()
5033 || !MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5034 }
5036 void post_work_verification() {
5037 assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5038 }
5040 // The parallel work done by all worker threads.
5041 void work(uint worker_id) {
5042 pre_work_verification();
5044 // Do first pass of code cache cleaning.
5045 _code_cache_task.work_first_pass(worker_id);
5047 // Let the threads mark that the first pass is done.
5048 _code_cache_task.barrier_mark(worker_id);
5050 // Clean the Strings and Symbols.
5051 _string_symbol_task.work(worker_id);
5053 // Wait for all workers to finish the first code cache cleaning pass.
5054 _code_cache_task.barrier_wait(worker_id);
5056 // Do the second code cache cleaning work, which realize on
5057 // the liveness information gathered during the first pass.
5058 _code_cache_task.work_second_pass(worker_id);
5060 // Clean all klasses that were not unloaded.
5061 _klass_cleaning_task.work();
5063 post_work_verification();
5064 }
5065 };
5068 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5069 bool process_strings,
5070 bool process_symbols,
5071 bool class_unloading_occurred) {
5072 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5073 workers()->active_workers() : 1);
5075 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5076 n_workers, class_unloading_occurred);
5077 if (G1CollectedHeap::use_parallel_gc_threads()) {
5078 set_par_threads(n_workers);
5079 workers()->run_task(&g1_unlink_task);
5080 set_par_threads(0);
5081 } else {
5082 g1_unlink_task.work(0);
5083 }
5084 }
5086 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5087 bool process_strings, bool process_symbols) {
5088 {
5089 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5090 _g1h->workers()->active_workers() : 1);
5091 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5092 if (G1CollectedHeap::use_parallel_gc_threads()) {
5093 set_par_threads(n_workers);
5094 workers()->run_task(&g1_unlink_task);
5095 set_par_threads(0);
5096 } else {
5097 g1_unlink_task.work(0);
5098 }
5099 }
5101 if (G1StringDedup::is_enabled()) {
5102 G1StringDedup::unlink(is_alive);
5103 }
5104 }
5106 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5107 private:
5108 DirtyCardQueueSet* _queue;
5109 public:
5110 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5112 virtual void work(uint worker_id) {
5113 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times();
5114 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
5116 RedirtyLoggedCardTableEntryClosure cl;
5117 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5118 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5119 } else {
5120 _queue->apply_closure_to_all_completed_buffers(&cl);
5121 }
5123 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed());
5124 }
5125 };
5127 void G1CollectedHeap::redirty_logged_cards() {
5128 double redirty_logged_cards_start = os::elapsedTime();
5130 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5131 _g1h->workers()->active_workers() : 1);
5133 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5134 dirty_card_queue_set().reset_for_par_iteration();
5135 if (use_parallel_gc_threads()) {
5136 set_par_threads(n_workers);
5137 workers()->run_task(&redirty_task);
5138 set_par_threads(0);
5139 } else {
5140 redirty_task.work(0);
5141 }
5143 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5144 dcq.merge_bufferlists(&dirty_card_queue_set());
5145 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5147 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5148 }
5150 // Weak Reference Processing support
5152 // An always "is_alive" closure that is used to preserve referents.
5153 // If the object is non-null then it's alive. Used in the preservation
5154 // of referent objects that are pointed to by reference objects
5155 // discovered by the CM ref processor.
5156 class G1AlwaysAliveClosure: public BoolObjectClosure {
5157 G1CollectedHeap* _g1;
5158 public:
5159 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5160 bool do_object_b(oop p) {
5161 if (p != NULL) {
5162 return true;
5163 }
5164 return false;
5165 }
5166 };
5168 bool G1STWIsAliveClosure::do_object_b(oop p) {
5169 // An object is reachable if it is outside the collection set,
5170 // or is inside and copied.
5171 return !_g1->obj_in_cs(p) || p->is_forwarded();
5172 }
5174 // Non Copying Keep Alive closure
5175 class G1KeepAliveClosure: public OopClosure {
5176 G1CollectedHeap* _g1;
5177 public:
5178 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5179 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5180 void do_oop(oop* p) {
5181 oop obj = *p;
5182 assert(obj != NULL, "the caller should have filtered out NULL values");
5184 const InCSetState cset_state = _g1->in_cset_state(obj);
5185 if (!cset_state.is_in_cset_or_humongous()) {
5186 return;
5187 }
5188 if (cset_state.is_in_cset()) {
5189 assert( obj->is_forwarded(), "invariant" );
5190 *p = obj->forwardee();
5191 } else {
5192 assert(!obj->is_forwarded(), "invariant" );
5193 assert(cset_state.is_humongous(),
5194 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
5195 _g1->set_humongous_is_live(obj);
5196 }
5197 }
5198 };
5200 // Copying Keep Alive closure - can be called from both
5201 // serial and parallel code as long as different worker
5202 // threads utilize different G1ParScanThreadState instances
5203 // and different queues.
5205 class G1CopyingKeepAliveClosure: public OopClosure {
5206 G1CollectedHeap* _g1h;
5207 OopClosure* _copy_non_heap_obj_cl;
5208 G1ParScanThreadState* _par_scan_state;
5210 public:
5211 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5212 OopClosure* non_heap_obj_cl,
5213 G1ParScanThreadState* pss):
5214 _g1h(g1h),
5215 _copy_non_heap_obj_cl(non_heap_obj_cl),
5216 _par_scan_state(pss)
5217 {}
5219 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5220 virtual void do_oop( oop* p) { do_oop_work(p); }
5222 template <class T> void do_oop_work(T* p) {
5223 oop obj = oopDesc::load_decode_heap_oop(p);
5225 if (_g1h->is_in_cset_or_humongous(obj)) {
5226 // If the referent object has been forwarded (either copied
5227 // to a new location or to itself in the event of an
5228 // evacuation failure) then we need to update the reference
5229 // field and, if both reference and referent are in the G1
5230 // heap, update the RSet for the referent.
5231 //
5232 // If the referent has not been forwarded then we have to keep
5233 // it alive by policy. Therefore we have copy the referent.
5234 //
5235 // If the reference field is in the G1 heap then we can push
5236 // on the PSS queue. When the queue is drained (after each
5237 // phase of reference processing) the object and it's followers
5238 // will be copied, the reference field set to point to the
5239 // new location, and the RSet updated. Otherwise we need to
5240 // use the the non-heap or metadata closures directly to copy
5241 // the referent object and update the pointer, while avoiding
5242 // updating the RSet.
5244 if (_g1h->is_in_g1_reserved(p)) {
5245 _par_scan_state->push_on_queue(p);
5246 } else {
5247 assert(!Metaspace::contains((const void*)p),
5248 err_msg("Unexpectedly found a pointer from metadata: "
5249 PTR_FORMAT, p));
5250 _copy_non_heap_obj_cl->do_oop(p);
5251 }
5252 }
5253 }
5254 };
5256 // Serial drain queue closure. Called as the 'complete_gc'
5257 // closure for each discovered list in some of the
5258 // reference processing phases.
5260 class G1STWDrainQueueClosure: public VoidClosure {
5261 protected:
5262 G1CollectedHeap* _g1h;
5263 G1ParScanThreadState* _par_scan_state;
5265 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5267 public:
5268 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5269 _g1h(g1h),
5270 _par_scan_state(pss)
5271 { }
5273 void do_void() {
5274 G1ParScanThreadState* const pss = par_scan_state();
5275 pss->trim_queue();
5276 }
5277 };
5279 // Parallel Reference Processing closures
5281 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5282 // processing during G1 evacuation pauses.
5284 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5285 private:
5286 G1CollectedHeap* _g1h;
5287 RefToScanQueueSet* _queues;
5288 FlexibleWorkGang* _workers;
5289 int _active_workers;
5291 public:
5292 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5293 FlexibleWorkGang* workers,
5294 RefToScanQueueSet *task_queues,
5295 int n_workers) :
5296 _g1h(g1h),
5297 _queues(task_queues),
5298 _workers(workers),
5299 _active_workers(n_workers)
5300 {
5301 assert(n_workers > 0, "shouldn't call this otherwise");
5302 }
5304 // Executes the given task using concurrent marking worker threads.
5305 virtual void execute(ProcessTask& task);
5306 virtual void execute(EnqueueTask& task);
5307 };
5309 // Gang task for possibly parallel reference processing
5311 class G1STWRefProcTaskProxy: public AbstractGangTask {
5312 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5313 ProcessTask& _proc_task;
5314 G1CollectedHeap* _g1h;
5315 RefToScanQueueSet *_task_queues;
5316 ParallelTaskTerminator* _terminator;
5318 public:
5319 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5320 G1CollectedHeap* g1h,
5321 RefToScanQueueSet *task_queues,
5322 ParallelTaskTerminator* terminator) :
5323 AbstractGangTask("Process reference objects in parallel"),
5324 _proc_task(proc_task),
5325 _g1h(g1h),
5326 _task_queues(task_queues),
5327 _terminator(terminator)
5328 {}
5330 virtual void work(uint worker_id) {
5331 // The reference processing task executed by a single worker.
5332 ResourceMark rm;
5333 HandleMark hm;
5335 G1STWIsAliveClosure is_alive(_g1h);
5337 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5338 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5340 pss.set_evac_failure_closure(&evac_failure_cl);
5342 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5344 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5346 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5348 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5349 // We also need to mark copied objects.
5350 copy_non_heap_cl = ©_mark_non_heap_cl;
5351 }
5353 // Keep alive closure.
5354 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5356 // Complete GC closure
5357 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5359 // Call the reference processing task's work routine.
5360 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5362 // Note we cannot assert that the refs array is empty here as not all
5363 // of the processing tasks (specifically phase2 - pp2_work) execute
5364 // the complete_gc closure (which ordinarily would drain the queue) so
5365 // the queue may not be empty.
5366 }
5367 };
5369 // Driver routine for parallel reference processing.
5370 // Creates an instance of the ref processing gang
5371 // task and has the worker threads execute it.
5372 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5373 assert(_workers != NULL, "Need parallel worker threads.");
5375 ParallelTaskTerminator terminator(_active_workers, _queues);
5376 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5378 _g1h->set_par_threads(_active_workers);
5379 _workers->run_task(&proc_task_proxy);
5380 _g1h->set_par_threads(0);
5381 }
5383 // Gang task for parallel reference enqueueing.
5385 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5386 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5387 EnqueueTask& _enq_task;
5389 public:
5390 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5391 AbstractGangTask("Enqueue reference objects in parallel"),
5392 _enq_task(enq_task)
5393 { }
5395 virtual void work(uint worker_id) {
5396 _enq_task.work(worker_id);
5397 }
5398 };
5400 // Driver routine for parallel reference enqueueing.
5401 // Creates an instance of the ref enqueueing gang
5402 // task and has the worker threads execute it.
5404 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5405 assert(_workers != NULL, "Need parallel worker threads.");
5407 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5409 _g1h->set_par_threads(_active_workers);
5410 _workers->run_task(&enq_task_proxy);
5411 _g1h->set_par_threads(0);
5412 }
5414 // End of weak reference support closures
5416 // Abstract task used to preserve (i.e. copy) any referent objects
5417 // that are in the collection set and are pointed to by reference
5418 // objects discovered by the CM ref processor.
5420 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5421 protected:
5422 G1CollectedHeap* _g1h;
5423 RefToScanQueueSet *_queues;
5424 ParallelTaskTerminator _terminator;
5425 uint _n_workers;
5427 public:
5428 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5429 AbstractGangTask("ParPreserveCMReferents"),
5430 _g1h(g1h),
5431 _queues(task_queues),
5432 _terminator(workers, _queues),
5433 _n_workers(workers)
5434 { }
5436 void work(uint worker_id) {
5437 ResourceMark rm;
5438 HandleMark hm;
5440 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5441 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5443 pss.set_evac_failure_closure(&evac_failure_cl);
5445 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5447 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5449 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5451 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5453 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5454 // We also need to mark copied objects.
5455 copy_non_heap_cl = ©_mark_non_heap_cl;
5456 }
5458 // Is alive closure
5459 G1AlwaysAliveClosure always_alive(_g1h);
5461 // Copying keep alive closure. Applied to referent objects that need
5462 // to be copied.
5463 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5465 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5467 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5468 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5470 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5471 // So this must be true - but assert just in case someone decides to
5472 // change the worker ids.
5473 assert(0 <= worker_id && worker_id < limit, "sanity");
5474 assert(!rp->discovery_is_atomic(), "check this code");
5476 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5477 for (uint idx = worker_id; idx < limit; idx += stride) {
5478 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5480 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5481 while (iter.has_next()) {
5482 // Since discovery is not atomic for the CM ref processor, we
5483 // can see some null referent objects.
5484 iter.load_ptrs(DEBUG_ONLY(true));
5485 oop ref = iter.obj();
5487 // This will filter nulls.
5488 if (iter.is_referent_alive()) {
5489 iter.make_referent_alive();
5490 }
5491 iter.move_to_next();
5492 }
5493 }
5495 // Drain the queue - which may cause stealing
5496 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5497 drain_queue.do_void();
5498 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5499 assert(pss.queue_is_empty(), "should be");
5500 }
5501 };
5503 // Weak Reference processing during an evacuation pause (part 1).
5504 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5505 double ref_proc_start = os::elapsedTime();
5507 ReferenceProcessor* rp = _ref_processor_stw;
5508 assert(rp->discovery_enabled(), "should have been enabled");
5510 // Any reference objects, in the collection set, that were 'discovered'
5511 // by the CM ref processor should have already been copied (either by
5512 // applying the external root copy closure to the discovered lists, or
5513 // by following an RSet entry).
5514 //
5515 // But some of the referents, that are in the collection set, that these
5516 // reference objects point to may not have been copied: the STW ref
5517 // processor would have seen that the reference object had already
5518 // been 'discovered' and would have skipped discovering the reference,
5519 // but would not have treated the reference object as a regular oop.
5520 // As a result the copy closure would not have been applied to the
5521 // referent object.
5522 //
5523 // We need to explicitly copy these referent objects - the references
5524 // will be processed at the end of remarking.
5525 //
5526 // We also need to do this copying before we process the reference
5527 // objects discovered by the STW ref processor in case one of these
5528 // referents points to another object which is also referenced by an
5529 // object discovered by the STW ref processor.
5531 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5532 no_of_gc_workers == workers()->active_workers(),
5533 "Need to reset active GC workers");
5535 set_par_threads(no_of_gc_workers);
5536 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5537 no_of_gc_workers,
5538 _task_queues);
5540 if (G1CollectedHeap::use_parallel_gc_threads()) {
5541 workers()->run_task(&keep_cm_referents);
5542 } else {
5543 keep_cm_referents.work(0);
5544 }
5546 set_par_threads(0);
5548 // Closure to test whether a referent is alive.
5549 G1STWIsAliveClosure is_alive(this);
5551 // Even when parallel reference processing is enabled, the processing
5552 // of JNI refs is serial and performed serially by the current thread
5553 // rather than by a worker. The following PSS will be used for processing
5554 // JNI refs.
5556 // Use only a single queue for this PSS.
5557 G1ParScanThreadState pss(this, 0, NULL);
5559 // We do not embed a reference processor in the copying/scanning
5560 // closures while we're actually processing the discovered
5561 // reference objects.
5562 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5564 pss.set_evac_failure_closure(&evac_failure_cl);
5566 assert(pss.queue_is_empty(), "pre-condition");
5568 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5570 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5572 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5574 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5575 // We also need to mark copied objects.
5576 copy_non_heap_cl = ©_mark_non_heap_cl;
5577 }
5579 // Keep alive closure.
5580 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5582 // Serial Complete GC closure
5583 G1STWDrainQueueClosure drain_queue(this, &pss);
5585 // Setup the soft refs policy...
5586 rp->setup_policy(false);
5588 ReferenceProcessorStats stats;
5589 if (!rp->processing_is_mt()) {
5590 // Serial reference processing...
5591 stats = rp->process_discovered_references(&is_alive,
5592 &keep_alive,
5593 &drain_queue,
5594 NULL,
5595 _gc_timer_stw,
5596 _gc_tracer_stw->gc_id());
5597 } else {
5598 // Parallel reference processing
5599 assert(rp->num_q() == no_of_gc_workers, "sanity");
5600 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5602 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5603 stats = rp->process_discovered_references(&is_alive,
5604 &keep_alive,
5605 &drain_queue,
5606 &par_task_executor,
5607 _gc_timer_stw,
5608 _gc_tracer_stw->gc_id());
5609 }
5611 _gc_tracer_stw->report_gc_reference_stats(stats);
5613 // We have completed copying any necessary live referent objects.
5614 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5616 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5617 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5618 }
5620 // Weak Reference processing during an evacuation pause (part 2).
5621 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5622 double ref_enq_start = os::elapsedTime();
5624 ReferenceProcessor* rp = _ref_processor_stw;
5625 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5627 // Now enqueue any remaining on the discovered lists on to
5628 // the pending list.
5629 if (!rp->processing_is_mt()) {
5630 // Serial reference processing...
5631 rp->enqueue_discovered_references();
5632 } else {
5633 // Parallel reference enqueueing
5635 assert(no_of_gc_workers == workers()->active_workers(),
5636 "Need to reset active workers");
5637 assert(rp->num_q() == no_of_gc_workers, "sanity");
5638 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5640 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5641 rp->enqueue_discovered_references(&par_task_executor);
5642 }
5644 rp->verify_no_references_recorded();
5645 assert(!rp->discovery_enabled(), "should have been disabled");
5647 // FIXME
5648 // CM's reference processing also cleans up the string and symbol tables.
5649 // Should we do that here also? We could, but it is a serial operation
5650 // and could significantly increase the pause time.
5652 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5653 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5654 }
5656 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5657 _expand_heap_after_alloc_failure = true;
5658 _evacuation_failed = false;
5660 // Should G1EvacuationFailureALot be in effect for this GC?
5661 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5663 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5665 // Disable the hot card cache.
5666 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5667 hot_card_cache->reset_hot_cache_claimed_index();
5668 hot_card_cache->set_use_cache(false);
5670 uint n_workers;
5671 if (G1CollectedHeap::use_parallel_gc_threads()) {
5672 n_workers =
5673 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5674 workers()->active_workers(),
5675 Threads::number_of_non_daemon_threads());
5676 assert(UseDynamicNumberOfGCThreads ||
5677 n_workers == workers()->total_workers(),
5678 "If not dynamic should be using all the workers");
5679 workers()->set_active_workers(n_workers);
5680 set_par_threads(n_workers);
5681 } else {
5682 assert(n_par_threads() == 0,
5683 "Should be the original non-parallel value");
5684 n_workers = 1;
5685 }
5688 init_for_evac_failure(NULL);
5690 rem_set()->prepare_for_younger_refs_iterate(true);
5692 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5693 double start_par_time_sec = os::elapsedTime();
5694 double end_par_time_sec;
5696 {
5697 G1RootProcessor root_processor(this);
5698 G1ParTask g1_par_task(this, _task_queues, &root_processor);
5699 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5700 if (g1_policy()->during_initial_mark_pause()) {
5701 ClassLoaderDataGraph::clear_claimed_marks();
5702 }
5704 if (G1CollectedHeap::use_parallel_gc_threads()) {
5705 // The individual threads will set their evac-failure closures.
5706 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5707 // These tasks use ShareHeap::_process_strong_tasks
5708 assert(UseDynamicNumberOfGCThreads ||
5709 workers()->active_workers() == workers()->total_workers(),
5710 "If not dynamic should be using all the workers");
5711 workers()->run_task(&g1_par_task);
5712 } else {
5713 g1_par_task.set_for_termination(n_workers);
5714 g1_par_task.work(0);
5715 }
5716 end_par_time_sec = os::elapsedTime();
5718 // Closing the inner scope will execute the destructor
5719 // for the G1RootProcessor object. We record the current
5720 // elapsed time before closing the scope so that time
5721 // taken for the destructor is NOT included in the
5722 // reported parallel time.
5723 }
5725 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
5727 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5728 phase_times->record_par_time(par_time_ms);
5730 double code_root_fixup_time_ms =
5731 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5732 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
5734 set_par_threads(0);
5736 // Process any discovered reference objects - we have
5737 // to do this _before_ we retire the GC alloc regions
5738 // as we may have to copy some 'reachable' referent
5739 // objects (and their reachable sub-graphs) that were
5740 // not copied during the pause.
5741 process_discovered_references(n_workers);
5743 if (G1StringDedup::is_enabled()) {
5744 double fixup_start = os::elapsedTime();
5746 G1STWIsAliveClosure is_alive(this);
5747 G1KeepAliveClosure keep_alive(this);
5748 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times);
5750 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
5751 phase_times->record_string_dedup_fixup_time(fixup_time_ms);
5752 }
5754 _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5755 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5757 // Reset and re-enable the hot card cache.
5758 // Note the counts for the cards in the regions in the
5759 // collection set are reset when the collection set is freed.
5760 hot_card_cache->reset_hot_cache();
5761 hot_card_cache->set_use_cache(true);
5763 purge_code_root_memory();
5765 if (g1_policy()->during_initial_mark_pause()) {
5766 // Reset the claim values set during marking the strong code roots
5767 reset_heap_region_claim_values();
5768 }
5770 finalize_for_evac_failure();
5772 if (evacuation_failed()) {
5773 remove_self_forwarding_pointers();
5775 // Reset the G1EvacuationFailureALot counters and flags
5776 // Note: the values are reset only when an actual
5777 // evacuation failure occurs.
5778 NOT_PRODUCT(reset_evacuation_should_fail();)
5779 }
5781 // Enqueue any remaining references remaining on the STW
5782 // reference processor's discovered lists. We need to do
5783 // this after the card table is cleaned (and verified) as
5784 // the act of enqueueing entries on to the pending list
5785 // will log these updates (and dirty their associated
5786 // cards). We need these updates logged to update any
5787 // RSets.
5788 enqueue_discovered_references(n_workers);
5790 redirty_logged_cards();
5791 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5792 }
5794 void G1CollectedHeap::free_region(HeapRegion* hr,
5795 FreeRegionList* free_list,
5796 bool par,
5797 bool locked) {
5798 assert(!hr->is_free(), "the region should not be free");
5799 assert(!hr->is_empty(), "the region should not be empty");
5800 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5801 assert(free_list != NULL, "pre-condition");
5803 if (G1VerifyBitmaps) {
5804 MemRegion mr(hr->bottom(), hr->end());
5805 concurrent_mark()->clearRangePrevBitmap(mr);
5806 }
5808 // Clear the card counts for this region.
5809 // Note: we only need to do this if the region is not young
5810 // (since we don't refine cards in young regions).
5811 if (!hr->is_young()) {
5812 _cg1r->hot_card_cache()->reset_card_counts(hr);
5813 }
5814 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5815 free_list->add_ordered(hr);
5816 }
5818 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5819 FreeRegionList* free_list,
5820 bool par) {
5821 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5822 assert(free_list != NULL, "pre-condition");
5824 size_t hr_capacity = hr->capacity();
5825 // We need to read this before we make the region non-humongous,
5826 // otherwise the information will be gone.
5827 uint last_index = hr->last_hc_index();
5828 hr->clear_humongous();
5829 free_region(hr, free_list, par);
5831 uint i = hr->hrm_index() + 1;
5832 while (i < last_index) {
5833 HeapRegion* curr_hr = region_at(i);
5834 assert(curr_hr->continuesHumongous(), "invariant");
5835 curr_hr->clear_humongous();
5836 free_region(curr_hr, free_list, par);
5837 i += 1;
5838 }
5839 }
5841 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5842 const HeapRegionSetCount& humongous_regions_removed) {
5843 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5844 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5845 _old_set.bulk_remove(old_regions_removed);
5846 _humongous_set.bulk_remove(humongous_regions_removed);
5847 }
5849 }
5851 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5852 assert(list != NULL, "list can't be null");
5853 if (!list->is_empty()) {
5854 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5855 _hrm.insert_list_into_free_list(list);
5856 }
5857 }
5859 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5860 _allocator->decrease_used(bytes);
5861 }
5863 class G1ParCleanupCTTask : public AbstractGangTask {
5864 G1SATBCardTableModRefBS* _ct_bs;
5865 G1CollectedHeap* _g1h;
5866 HeapRegion* volatile _su_head;
5867 public:
5868 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5869 G1CollectedHeap* g1h) :
5870 AbstractGangTask("G1 Par Cleanup CT Task"),
5871 _ct_bs(ct_bs), _g1h(g1h) { }
5873 void work(uint worker_id) {
5874 HeapRegion* r;
5875 while (r = _g1h->pop_dirty_cards_region()) {
5876 clear_cards(r);
5877 }
5878 }
5880 void clear_cards(HeapRegion* r) {
5881 // Cards of the survivors should have already been dirtied.
5882 if (!r->is_survivor()) {
5883 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5884 }
5885 }
5886 };
5888 #ifndef PRODUCT
5889 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5890 G1CollectedHeap* _g1h;
5891 G1SATBCardTableModRefBS* _ct_bs;
5892 public:
5893 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5894 : _g1h(g1h), _ct_bs(ct_bs) { }
5895 virtual bool doHeapRegion(HeapRegion* r) {
5896 if (r->is_survivor()) {
5897 _g1h->verify_dirty_region(r);
5898 } else {
5899 _g1h->verify_not_dirty_region(r);
5900 }
5901 return false;
5902 }
5903 };
5905 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5906 // All of the region should be clean.
5907 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5908 MemRegion mr(hr->bottom(), hr->end());
5909 ct_bs->verify_not_dirty_region(mr);
5910 }
5912 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5913 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5914 // dirty allocated blocks as they allocate them. The thread that
5915 // retires each region and replaces it with a new one will do a
5916 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5917 // not dirty that area (one less thing to have to do while holding
5918 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5919 // is dirty.
5920 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5921 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5922 if (hr->is_young()) {
5923 ct_bs->verify_g1_young_region(mr);
5924 } else {
5925 ct_bs->verify_dirty_region(mr);
5926 }
5927 }
5929 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5930 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5931 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5932 verify_dirty_region(hr);
5933 }
5934 }
5936 void G1CollectedHeap::verify_dirty_young_regions() {
5937 verify_dirty_young_list(_young_list->first_region());
5938 }
5940 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5941 HeapWord* tams, HeapWord* end) {
5942 guarantee(tams <= end,
5943 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
5944 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5945 if (result < end) {
5946 gclog_or_tty->cr();
5947 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5948 bitmap_name, result);
5949 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5950 bitmap_name, tams, end);
5951 return false;
5952 }
5953 return true;
5954 }
5956 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5957 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5958 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5960 HeapWord* bottom = hr->bottom();
5961 HeapWord* ptams = hr->prev_top_at_mark_start();
5962 HeapWord* ntams = hr->next_top_at_mark_start();
5963 HeapWord* end = hr->end();
5965 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
5967 bool res_n = true;
5968 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
5969 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
5970 // if we happen to be in that state.
5971 if (mark_in_progress() || !_cmThread->in_progress()) {
5972 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
5973 }
5974 if (!res_p || !res_n) {
5975 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5976 HR_FORMAT_PARAMS(hr));
5977 gclog_or_tty->print_cr("#### Caller: %s", caller);
5978 return false;
5979 }
5980 return true;
5981 }
5983 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5984 if (!G1VerifyBitmaps) return;
5986 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5987 }
5989 class G1VerifyBitmapClosure : public HeapRegionClosure {
5990 private:
5991 const char* _caller;
5992 G1CollectedHeap* _g1h;
5993 bool _failures;
5995 public:
5996 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5997 _caller(caller), _g1h(g1h), _failures(false) { }
5999 bool failures() { return _failures; }
6001 virtual bool doHeapRegion(HeapRegion* hr) {
6002 if (hr->continuesHumongous()) return false;
6004 bool result = _g1h->verify_bitmaps(_caller, hr);
6005 if (!result) {
6006 _failures = true;
6007 }
6008 return false;
6009 }
6010 };
6012 void G1CollectedHeap::check_bitmaps(const char* caller) {
6013 if (!G1VerifyBitmaps) return;
6015 G1VerifyBitmapClosure cl(caller, this);
6016 heap_region_iterate(&cl);
6017 guarantee(!cl.failures(), "bitmap verification");
6018 }
6020 bool G1CollectedHeap::check_cset_fast_test() {
6021 bool failures = false;
6022 for (uint i = 0; i < _hrm.length(); i += 1) {
6023 HeapRegion* hr = _hrm.at(i);
6024 InCSetState cset_state = (InCSetState) _in_cset_fast_test.get_by_index((uint) i);
6025 if (hr->isHumongous()) {
6026 if (hr->in_collection_set()) {
6027 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
6028 failures = true;
6029 break;
6030 }
6031 if (cset_state.is_in_cset()) {
6032 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
6033 failures = true;
6034 break;
6035 }
6036 if (hr->continuesHumongous() && cset_state.is_humongous()) {
6037 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
6038 failures = true;
6039 break;
6040 }
6041 } else {
6042 if (cset_state.is_humongous()) {
6043 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
6044 failures = true;
6045 break;
6046 }
6047 if (hr->in_collection_set() != cset_state.is_in_cset()) {
6048 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
6049 hr->in_collection_set(), cset_state.value(), i);
6050 failures = true;
6051 break;
6052 }
6053 if (cset_state.is_in_cset()) {
6054 if (hr->is_young() != (cset_state.is_young())) {
6055 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
6056 hr->is_young(), cset_state.value(), i);
6057 failures = true;
6058 break;
6059 }
6060 if (hr->is_old() != (cset_state.is_old())) {
6061 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
6062 hr->is_old(), cset_state.value(), i);
6063 failures = true;
6064 break;
6065 }
6066 }
6067 }
6068 }
6069 return !failures;
6070 }
6071 #endif // PRODUCT
6073 void G1CollectedHeap::cleanUpCardTable() {
6074 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6075 double start = os::elapsedTime();
6077 {
6078 // Iterate over the dirty cards region list.
6079 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6081 if (G1CollectedHeap::use_parallel_gc_threads()) {
6082 set_par_threads();
6083 workers()->run_task(&cleanup_task);
6084 set_par_threads(0);
6085 } else {
6086 while (_dirty_cards_region_list) {
6087 HeapRegion* r = _dirty_cards_region_list;
6088 cleanup_task.clear_cards(r);
6089 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6090 if (_dirty_cards_region_list == r) {
6091 // The last region.
6092 _dirty_cards_region_list = NULL;
6093 }
6094 r->set_next_dirty_cards_region(NULL);
6095 }
6096 }
6097 #ifndef PRODUCT
6098 if (G1VerifyCTCleanup || VerifyAfterGC) {
6099 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6100 heap_region_iterate(&cleanup_verifier);
6101 }
6102 #endif
6103 }
6105 double elapsed = os::elapsedTime() - start;
6106 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6107 }
6109 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6110 size_t pre_used = 0;
6111 FreeRegionList local_free_list("Local List for CSet Freeing");
6113 double young_time_ms = 0.0;
6114 double non_young_time_ms = 0.0;
6116 // Since the collection set is a superset of the the young list,
6117 // all we need to do to clear the young list is clear its
6118 // head and length, and unlink any young regions in the code below
6119 _young_list->clear();
6121 G1CollectorPolicy* policy = g1_policy();
6123 double start_sec = os::elapsedTime();
6124 bool non_young = true;
6126 HeapRegion* cur = cs_head;
6127 int age_bound = -1;
6128 size_t rs_lengths = 0;
6130 while (cur != NULL) {
6131 assert(!is_on_master_free_list(cur), "sanity");
6132 if (non_young) {
6133 if (cur->is_young()) {
6134 double end_sec = os::elapsedTime();
6135 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6136 non_young_time_ms += elapsed_ms;
6138 start_sec = os::elapsedTime();
6139 non_young = false;
6140 }
6141 } else {
6142 if (!cur->is_young()) {
6143 double end_sec = os::elapsedTime();
6144 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6145 young_time_ms += elapsed_ms;
6147 start_sec = os::elapsedTime();
6148 non_young = true;
6149 }
6150 }
6152 rs_lengths += cur->rem_set()->occupied_locked();
6154 HeapRegion* next = cur->next_in_collection_set();
6155 assert(cur->in_collection_set(), "bad CS");
6156 cur->set_next_in_collection_set(NULL);
6157 cur->set_in_collection_set(false);
6159 if (cur->is_young()) {
6160 int index = cur->young_index_in_cset();
6161 assert(index != -1, "invariant");
6162 assert((uint) index < policy->young_cset_region_length(), "invariant");
6163 size_t words_survived = _surviving_young_words[index];
6164 cur->record_surv_words_in_group(words_survived);
6166 // At this point the we have 'popped' cur from the collection set
6167 // (linked via next_in_collection_set()) but it is still in the
6168 // young list (linked via next_young_region()). Clear the
6169 // _next_young_region field.
6170 cur->set_next_young_region(NULL);
6171 } else {
6172 int index = cur->young_index_in_cset();
6173 assert(index == -1, "invariant");
6174 }
6176 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6177 (!cur->is_young() && cur->young_index_in_cset() == -1),
6178 "invariant" );
6180 if (!cur->evacuation_failed()) {
6181 MemRegion used_mr = cur->used_region();
6183 // And the region is empty.
6184 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6185 pre_used += cur->used();
6186 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6187 } else {
6188 cur->uninstall_surv_rate_group();
6189 if (cur->is_young()) {
6190 cur->set_young_index_in_cset(-1);
6191 }
6192 cur->set_evacuation_failed(false);
6193 // The region is now considered to be old.
6194 cur->set_old();
6195 _old_set.add(cur);
6196 evacuation_info.increment_collectionset_used_after(cur->used());
6197 }
6198 cur = next;
6199 }
6201 evacuation_info.set_regions_freed(local_free_list.length());
6202 policy->record_max_rs_lengths(rs_lengths);
6203 policy->cset_regions_freed();
6205 double end_sec = os::elapsedTime();
6206 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6208 if (non_young) {
6209 non_young_time_ms += elapsed_ms;
6210 } else {
6211 young_time_ms += elapsed_ms;
6212 }
6214 prepend_to_freelist(&local_free_list);
6215 decrement_summary_bytes(pre_used);
6216 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6217 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6218 }
6220 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6221 private:
6222 FreeRegionList* _free_region_list;
6223 HeapRegionSet* _proxy_set;
6224 HeapRegionSetCount _humongous_regions_removed;
6225 size_t _freed_bytes;
6226 public:
6228 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6229 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6230 }
6232 virtual bool doHeapRegion(HeapRegion* r) {
6233 if (!r->startsHumongous()) {
6234 return false;
6235 }
6237 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6239 oop obj = (oop)r->bottom();
6240 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6242 // The following checks whether the humongous object is live are sufficient.
6243 // The main additional check (in addition to having a reference from the roots
6244 // or the young gen) is whether the humongous object has a remembered set entry.
6245 //
6246 // A humongous object cannot be live if there is no remembered set for it
6247 // because:
6248 // - there can be no references from within humongous starts regions referencing
6249 // the object because we never allocate other objects into them.
6250 // (I.e. there are no intra-region references that may be missed by the
6251 // remembered set)
6252 // - as soon there is a remembered set entry to the humongous starts region
6253 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6254 // until the end of a concurrent mark.
6255 //
6256 // It is not required to check whether the object has been found dead by marking
6257 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6258 // all objects allocated during that time are considered live.
6259 // SATB marking is even more conservative than the remembered set.
6260 // So if at this point in the collection there is no remembered set entry,
6261 // nobody has a reference to it.
6262 // At the start of collection we flush all refinement logs, and remembered sets
6263 // are completely up-to-date wrt to references to the humongous object.
6264 //
6265 // Other implementation considerations:
6266 // - never consider object arrays: while they are a valid target, they have not
6267 // been observed to be used as temporary objects.
6268 // - they would also pose considerable effort for cleaning up the the remembered
6269 // sets.
6270 // While this cleanup is not strictly necessary to be done (or done instantly),
6271 // given that their occurrence is very low, this saves us this additional
6272 // complexity.
6273 uint region_idx = r->hrm_index();
6274 if (g1h->humongous_is_live(region_idx) ||
6275 g1h->humongous_region_is_always_live(region_idx)) {
6277 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6278 gclog_or_tty->print_cr("Live humongous %d region %d size "SIZE_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6279 r->isHumongous(),
6280 region_idx,
6281 obj->size()*HeapWordSize,
6282 r->rem_set()->occupied(),
6283 r->rem_set()->strong_code_roots_list_length(),
6284 next_bitmap->isMarked(r->bottom()),
6285 g1h->humongous_is_live(region_idx),
6286 obj->is_objArray()
6287 );
6288 }
6290 return false;
6291 }
6293 guarantee(!obj->is_objArray(),
6294 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6295 r->bottom()));
6297 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6298 gclog_or_tty->print_cr("Reclaim humongous region %d size "SIZE_FORMAT" start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other ",
6299 r->isHumongous(),
6300 obj->size()*HeapWordSize,
6301 r->bottom(),
6302 region_idx,
6303 r->region_num(),
6304 r->rem_set()->occupied(),
6305 r->rem_set()->strong_code_roots_list_length(),
6306 next_bitmap->isMarked(r->bottom()),
6307 g1h->humongous_is_live(region_idx),
6308 obj->is_objArray()
6309 );
6310 }
6311 // Need to clear mark bit of the humongous object if already set.
6312 if (next_bitmap->isMarked(r->bottom())) {
6313 next_bitmap->clear(r->bottom());
6314 }
6315 _freed_bytes += r->used();
6316 r->set_containing_set(NULL);
6317 _humongous_regions_removed.increment(1u, r->capacity());
6318 g1h->free_humongous_region(r, _free_region_list, false);
6320 return false;
6321 }
6323 HeapRegionSetCount& humongous_free_count() {
6324 return _humongous_regions_removed;
6325 }
6327 size_t bytes_freed() const {
6328 return _freed_bytes;
6329 }
6331 size_t humongous_reclaimed() const {
6332 return _humongous_regions_removed.length();
6333 }
6334 };
6336 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6337 assert_at_safepoint(true);
6339 if (!G1ReclaimDeadHumongousObjectsAtYoungGC ||
6340 (!_has_humongous_reclaim_candidates && !G1TraceReclaimDeadHumongousObjectsAtYoungGC)) {
6341 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6342 return;
6343 }
6345 double start_time = os::elapsedTime();
6347 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6349 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6350 heap_region_iterate(&cl);
6352 HeapRegionSetCount empty_set;
6353 remove_from_old_sets(empty_set, cl.humongous_free_count());
6355 G1HRPrinter* hr_printer = _g1h->hr_printer();
6356 if (hr_printer->is_active()) {
6357 FreeRegionListIterator iter(&local_cleanup_list);
6358 while (iter.more_available()) {
6359 HeapRegion* hr = iter.get_next();
6360 hr_printer->cleanup(hr);
6361 }
6362 }
6364 prepend_to_freelist(&local_cleanup_list);
6365 decrement_summary_bytes(cl.bytes_freed());
6367 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6368 cl.humongous_reclaimed());
6369 }
6371 // This routine is similar to the above but does not record
6372 // any policy statistics or update free lists; we are abandoning
6373 // the current incremental collection set in preparation of a
6374 // full collection. After the full GC we will start to build up
6375 // the incremental collection set again.
6376 // This is only called when we're doing a full collection
6377 // and is immediately followed by the tearing down of the young list.
6379 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6380 HeapRegion* cur = cs_head;
6382 while (cur != NULL) {
6383 HeapRegion* next = cur->next_in_collection_set();
6384 assert(cur->in_collection_set(), "bad CS");
6385 cur->set_next_in_collection_set(NULL);
6386 cur->set_in_collection_set(false);
6387 cur->set_young_index_in_cset(-1);
6388 cur = next;
6389 }
6390 }
6392 void G1CollectedHeap::set_free_regions_coming() {
6393 if (G1ConcRegionFreeingVerbose) {
6394 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6395 "setting free regions coming");
6396 }
6398 assert(!free_regions_coming(), "pre-condition");
6399 _free_regions_coming = true;
6400 }
6402 void G1CollectedHeap::reset_free_regions_coming() {
6403 assert(free_regions_coming(), "pre-condition");
6405 {
6406 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6407 _free_regions_coming = false;
6408 SecondaryFreeList_lock->notify_all();
6409 }
6411 if (G1ConcRegionFreeingVerbose) {
6412 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6413 "reset free regions coming");
6414 }
6415 }
6417 void G1CollectedHeap::wait_while_free_regions_coming() {
6418 // Most of the time we won't have to wait, so let's do a quick test
6419 // first before we take the lock.
6420 if (!free_regions_coming()) {
6421 return;
6422 }
6424 if (G1ConcRegionFreeingVerbose) {
6425 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6426 "waiting for free regions");
6427 }
6429 {
6430 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6431 while (free_regions_coming()) {
6432 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6433 }
6434 }
6436 if (G1ConcRegionFreeingVerbose) {
6437 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6438 "done waiting for free regions");
6439 }
6440 }
6442 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6443 assert(heap_lock_held_for_gc(),
6444 "the heap lock should already be held by or for this thread");
6445 _young_list->push_region(hr);
6446 }
6448 class NoYoungRegionsClosure: public HeapRegionClosure {
6449 private:
6450 bool _success;
6451 public:
6452 NoYoungRegionsClosure() : _success(true) { }
6453 bool doHeapRegion(HeapRegion* r) {
6454 if (r->is_young()) {
6455 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6456 r->bottom(), r->end());
6457 _success = false;
6458 }
6459 return false;
6460 }
6461 bool success() { return _success; }
6462 };
6464 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6465 bool ret = _young_list->check_list_empty(check_sample);
6467 if (check_heap) {
6468 NoYoungRegionsClosure closure;
6469 heap_region_iterate(&closure);
6470 ret = ret && closure.success();
6471 }
6473 return ret;
6474 }
6476 class TearDownRegionSetsClosure : public HeapRegionClosure {
6477 private:
6478 HeapRegionSet *_old_set;
6480 public:
6481 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6483 bool doHeapRegion(HeapRegion* r) {
6484 if (r->is_old()) {
6485 _old_set->remove(r);
6486 } else {
6487 // We ignore free regions, we'll empty the free list afterwards.
6488 // We ignore young regions, we'll empty the young list afterwards.
6489 // We ignore humongous regions, we're not tearing down the
6490 // humongous regions set.
6491 assert(r->is_free() || r->is_young() || r->isHumongous(),
6492 "it cannot be another type");
6493 }
6494 return false;
6495 }
6497 ~TearDownRegionSetsClosure() {
6498 assert(_old_set->is_empty(), "post-condition");
6499 }
6500 };
6502 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6503 assert_at_safepoint(true /* should_be_vm_thread */);
6505 if (!free_list_only) {
6506 TearDownRegionSetsClosure cl(&_old_set);
6507 heap_region_iterate(&cl);
6509 // Note that emptying the _young_list is postponed and instead done as
6510 // the first step when rebuilding the regions sets again. The reason for
6511 // this is that during a full GC string deduplication needs to know if
6512 // a collected region was young or old when the full GC was initiated.
6513 }
6514 _hrm.remove_all_free_regions();
6515 }
6517 class RebuildRegionSetsClosure : public HeapRegionClosure {
6518 private:
6519 bool _free_list_only;
6520 HeapRegionSet* _old_set;
6521 HeapRegionManager* _hrm;
6522 size_t _total_used;
6524 public:
6525 RebuildRegionSetsClosure(bool free_list_only,
6526 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6527 _free_list_only(free_list_only),
6528 _old_set(old_set), _hrm(hrm), _total_used(0) {
6529 assert(_hrm->num_free_regions() == 0, "pre-condition");
6530 if (!free_list_only) {
6531 assert(_old_set->is_empty(), "pre-condition");
6532 }
6533 }
6535 bool doHeapRegion(HeapRegion* r) {
6536 if (r->continuesHumongous()) {
6537 return false;
6538 }
6540 if (r->is_empty()) {
6541 // Add free regions to the free list
6542 r->set_free();
6543 r->set_allocation_context(AllocationContext::system());
6544 _hrm->insert_into_free_list(r);
6545 } else if (!_free_list_only) {
6546 assert(!r->is_young(), "we should not come across young regions");
6548 if (r->isHumongous()) {
6549 // We ignore humongous regions, we left the humongous set unchanged
6550 } else {
6551 // Objects that were compacted would have ended up on regions
6552 // that were previously old or free.
6553 assert(r->is_free() || r->is_old(), "invariant");
6554 // We now consider them old, so register as such.
6555 r->set_old();
6556 _old_set->add(r);
6557 }
6558 _total_used += r->used();
6559 }
6561 return false;
6562 }
6564 size_t total_used() {
6565 return _total_used;
6566 }
6567 };
6569 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6570 assert_at_safepoint(true /* should_be_vm_thread */);
6572 if (!free_list_only) {
6573 _young_list->empty_list();
6574 }
6576 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6577 heap_region_iterate(&cl);
6579 if (!free_list_only) {
6580 _allocator->set_used(cl.total_used());
6581 }
6582 assert(_allocator->used_unlocked() == recalculate_used(),
6583 err_msg("inconsistent _allocator->used_unlocked(), "
6584 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6585 _allocator->used_unlocked(), recalculate_used()));
6586 }
6588 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6589 _refine_cte_cl->set_concurrent(concurrent);
6590 }
6592 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6593 HeapRegion* hr = heap_region_containing(p);
6594 return hr->is_in(p);
6595 }
6597 // Methods for the mutator alloc region
6599 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6600 bool force) {
6601 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6602 assert(!force || g1_policy()->can_expand_young_list(),
6603 "if force is true we should be able to expand the young list");
6604 bool young_list_full = g1_policy()->is_young_list_full();
6605 if (force || !young_list_full) {
6606 HeapRegion* new_alloc_region = new_region(word_size,
6607 false /* is_old */,
6608 false /* do_expand */);
6609 if (new_alloc_region != NULL) {
6610 set_region_short_lived_locked(new_alloc_region);
6611 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6612 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6613 return new_alloc_region;
6614 }
6615 }
6616 return NULL;
6617 }
6619 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6620 size_t allocated_bytes) {
6621 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6622 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6624 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6625 _allocator->increase_used(allocated_bytes);
6626 _hr_printer.retire(alloc_region);
6627 // We update the eden sizes here, when the region is retired,
6628 // instead of when it's allocated, since this is the point that its
6629 // used space has been recored in _summary_bytes_used.
6630 g1mm()->update_eden_size();
6631 }
6633 void G1CollectedHeap::set_par_threads() {
6634 // Don't change the number of workers. Use the value previously set
6635 // in the workgroup.
6636 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6637 uint n_workers = workers()->active_workers();
6638 assert(UseDynamicNumberOfGCThreads ||
6639 n_workers == workers()->total_workers(),
6640 "Otherwise should be using the total number of workers");
6641 if (n_workers == 0) {
6642 assert(false, "Should have been set in prior evacuation pause.");
6643 n_workers = ParallelGCThreads;
6644 workers()->set_active_workers(n_workers);
6645 }
6646 set_par_threads(n_workers);
6647 }
6649 // Methods for the GC alloc regions
6651 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6652 uint count,
6653 InCSetState dest) {
6654 assert(FreeList_lock->owned_by_self(), "pre-condition");
6656 if (count < g1_policy()->max_regions(dest)) {
6657 const bool is_survivor = (dest.is_young());
6658 HeapRegion* new_alloc_region = new_region(word_size,
6659 !is_survivor,
6660 true /* do_expand */);
6661 if (new_alloc_region != NULL) {
6662 // We really only need to do this for old regions given that we
6663 // should never scan survivors. But it doesn't hurt to do it
6664 // for survivors too.
6665 new_alloc_region->record_timestamp();
6666 if (is_survivor) {
6667 new_alloc_region->set_survivor();
6668 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6669 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6670 } else {
6671 new_alloc_region->set_old();
6672 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6673 check_bitmaps("Old Region Allocation", new_alloc_region);
6674 }
6675 bool during_im = g1_policy()->during_initial_mark_pause();
6676 new_alloc_region->note_start_of_copying(during_im);
6677 return new_alloc_region;
6678 }
6679 }
6680 return NULL;
6681 }
6683 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6684 size_t allocated_bytes,
6685 InCSetState dest) {
6686 bool during_im = g1_policy()->during_initial_mark_pause();
6687 alloc_region->note_end_of_copying(during_im);
6688 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6689 if (dest.is_young()) {
6690 young_list()->add_survivor_region(alloc_region);
6691 } else {
6692 _old_set.add(alloc_region);
6693 }
6694 _hr_printer.retire(alloc_region);
6695 }
6697 // Heap region set verification
6699 class VerifyRegionListsClosure : public HeapRegionClosure {
6700 private:
6701 HeapRegionSet* _old_set;
6702 HeapRegionSet* _humongous_set;
6703 HeapRegionManager* _hrm;
6705 public:
6706 HeapRegionSetCount _old_count;
6707 HeapRegionSetCount _humongous_count;
6708 HeapRegionSetCount _free_count;
6710 VerifyRegionListsClosure(HeapRegionSet* old_set,
6711 HeapRegionSet* humongous_set,
6712 HeapRegionManager* hrm) :
6713 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6714 _old_count(), _humongous_count(), _free_count(){ }
6716 bool doHeapRegion(HeapRegion* hr) {
6717 if (hr->continuesHumongous()) {
6718 return false;
6719 }
6721 if (hr->is_young()) {
6722 // TODO
6723 } else if (hr->startsHumongous()) {
6724 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6725 _humongous_count.increment(1u, hr->capacity());
6726 } else if (hr->is_empty()) {
6727 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6728 _free_count.increment(1u, hr->capacity());
6729 } else if (hr->is_old()) {
6730 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6731 _old_count.increment(1u, hr->capacity());
6732 } else {
6733 ShouldNotReachHere();
6734 }
6735 return false;
6736 }
6738 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6739 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6740 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6741 old_set->total_capacity_bytes(), _old_count.capacity()));
6743 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6744 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6745 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6747 guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length()));
6748 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6749 free_list->total_capacity_bytes(), _free_count.capacity()));
6750 }
6751 };
6753 void G1CollectedHeap::verify_region_sets() {
6754 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6756 // First, check the explicit lists.
6757 _hrm.verify();
6758 {
6759 // Given that a concurrent operation might be adding regions to
6760 // the secondary free list we have to take the lock before
6761 // verifying it.
6762 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6763 _secondary_free_list.verify_list();
6764 }
6766 // If a concurrent region freeing operation is in progress it will
6767 // be difficult to correctly attributed any free regions we come
6768 // across to the correct free list given that they might belong to
6769 // one of several (free_list, secondary_free_list, any local lists,
6770 // etc.). So, if that's the case we will skip the rest of the
6771 // verification operation. Alternatively, waiting for the concurrent
6772 // operation to complete will have a non-trivial effect on the GC's
6773 // operation (no concurrent operation will last longer than the
6774 // interval between two calls to verification) and it might hide
6775 // any issues that we would like to catch during testing.
6776 if (free_regions_coming()) {
6777 return;
6778 }
6780 // Make sure we append the secondary_free_list on the free_list so
6781 // that all free regions we will come across can be safely
6782 // attributed to the free_list.
6783 append_secondary_free_list_if_not_empty_with_lock();
6785 // Finally, make sure that the region accounting in the lists is
6786 // consistent with what we see in the heap.
6788 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6789 heap_region_iterate(&cl);
6790 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6791 }
6793 // Optimized nmethod scanning
6795 class RegisterNMethodOopClosure: public OopClosure {
6796 G1CollectedHeap* _g1h;
6797 nmethod* _nm;
6799 template <class T> void do_oop_work(T* p) {
6800 T heap_oop = oopDesc::load_heap_oop(p);
6801 if (!oopDesc::is_null(heap_oop)) {
6802 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6803 HeapRegion* hr = _g1h->heap_region_containing(obj);
6804 assert(!hr->continuesHumongous(),
6805 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6806 " starting at "HR_FORMAT,
6807 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6809 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6810 hr->add_strong_code_root_locked(_nm);
6811 }
6812 }
6814 public:
6815 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6816 _g1h(g1h), _nm(nm) {}
6818 void do_oop(oop* p) { do_oop_work(p); }
6819 void do_oop(narrowOop* p) { do_oop_work(p); }
6820 };
6822 class UnregisterNMethodOopClosure: public OopClosure {
6823 G1CollectedHeap* _g1h;
6824 nmethod* _nm;
6826 template <class T> void do_oop_work(T* p) {
6827 T heap_oop = oopDesc::load_heap_oop(p);
6828 if (!oopDesc::is_null(heap_oop)) {
6829 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6830 HeapRegion* hr = _g1h->heap_region_containing(obj);
6831 assert(!hr->continuesHumongous(),
6832 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6833 " starting at "HR_FORMAT,
6834 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6836 hr->remove_strong_code_root(_nm);
6837 }
6838 }
6840 public:
6841 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6842 _g1h(g1h), _nm(nm) {}
6844 void do_oop(oop* p) { do_oop_work(p); }
6845 void do_oop(narrowOop* p) { do_oop_work(p); }
6846 };
6848 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6849 CollectedHeap::register_nmethod(nm);
6851 guarantee(nm != NULL, "sanity");
6852 RegisterNMethodOopClosure reg_cl(this, nm);
6853 nm->oops_do(®_cl);
6854 }
6856 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6857 CollectedHeap::unregister_nmethod(nm);
6859 guarantee(nm != NULL, "sanity");
6860 UnregisterNMethodOopClosure reg_cl(this, nm);
6861 nm->oops_do(®_cl, true);
6862 }
6864 void G1CollectedHeap::purge_code_root_memory() {
6865 double purge_start = os::elapsedTime();
6866 G1CodeRootSet::purge();
6867 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6868 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6869 }
6871 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6872 G1CollectedHeap* _g1h;
6874 public:
6875 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6876 _g1h(g1h) {}
6878 void do_code_blob(CodeBlob* cb) {
6879 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6880 if (nm == NULL) {
6881 return;
6882 }
6884 if (ScavengeRootsInCode) {
6885 _g1h->register_nmethod(nm);
6886 }
6887 }
6888 };
6890 void G1CollectedHeap::rebuild_strong_code_roots() {
6891 RebuildStrongCodeRootClosure blob_cl(this);
6892 CodeCache::blobs_do(&blob_cl);
6893 }